Good introductory books on LGBT Law for EPQ?

There is no such thing as "LGBT discrimination law". Under the Equality Act 2010, sex is a protected characteristic, sexual orientation is a protected characteristic, and gender reassignment is a protected characteristic. Gender identity is not a protected characteristic, despite claims to the contrary by some activist organisations.
The Supreme Court will shortly rule on whether sex means biological sex, or if the plain and obvious meaning of sex is obscured by the Gender Recognition Act 2004, an ill thought-out and carelessly drafted statute. Parliament may have to legislate to clarify the meaning of sex, in order to avoid the consequences that have ensued in Australia in the Tickle v Giggle case, which deprives women of legal protection and in effect abolishes women as a class of legal person.
The books to look at are general books about discrimination law and human rights. Have a look at all of the cases which have followed Forstater, and note that the Jaguar Land Rover case is not binding on any court or tribunal. The decision in that case is generally regarded as wrong by practitioners familiar with the relevant law.
The book edited by Ashford and Maine is a shameful example of academic charlatanry. It wilfully misrepresents the law for ideological reasons. The so called practical book by White and Newbegin is also a work of activism and is mostly tosh (see Naomi Cunningham's coruscating review of that book on the Legal Feminist blog, and see also Grammar and Grievance, Ms Cunningham's article about pronouns).

Thank you. Sorry, I should have clarified that I meant the Equality Act 2010 (referring to it as LGBT discrimination law was only for ease of title for my project).
This might be a stupid question, but why is gender identity separate to gender reassignment? If the Equality Act considers proposing to undergo gender reassignment as meeting the criteria for gender reassignment, how is that different to having a different gender identity (e.g. if someone wishes to transition to male to female, surely they are proposing to undergo reassignment?).
Thank you again for the help (I will stay clear of the books in that case!).

Gender assignment has a technical meaning, set out in the legislation, and relatively few of those who claim to possess a gender identity have sought or are seeking gender reassignment within the meaning of the legislation.
Gender identity is not a term that has any legal meaning, or indeed any clearly understood non-legal meaning. Some people claim that there are over one hundred identities, and some claim to have more than one of these, or to change their identity from day to day.
Gender identity is a contentious concept referring to a claimed subjective state of mind or emotion, which neither science nor the law can evaluate.
Activists have sought to obscure the clarity of the law (by for example publishing the books mentioned above), but the 2010 Act is clear. The GRA, however, is a dog's breakfast of incoherent drafting.
Not law books, but two very good books to read on the subject in general: Material Girls, by Kathleen Stock, and Time To Think by Hannah Barnes. Many people find that reading those books is a wake up and smell the coffee moment.

I am a Y13 student who is currently doing an EPQ on the conflict between the manifestation of religious freedom and LGBT discrimination law, and very much struggling to find decent books on this topic.
So far, I have looked at some judgements (Lee v Ashers, Eweida and Forstater). However, we are expected to have a variety of sources for the project, including books. I initially decided on Gender, Sexuality and Law (by Ashford and Maine), but am reconsidering after having read some rather scathing reviews of it online. The other one I have looked at is Gender Recognition and the Law (by Flora Renz). I am yet to commit to either book, and have yet to find other books on the topic.
I am finding it difficult to separate the books that offer a legal perspective as opposed to a social or political commentary, and was wondering if anyone had any book recommendations/advice?

I'm not sure about books but the podcast Law and Disorder has an episodes about the history of laws on homosexuality. The podcast hosts are prominent legal figures and they bring in guests who have in depth knowledge on the topic who also mention a book I think. I would recommend giving it a listen!

Two founders of Stonewall who now run LGB Alliance have told me that Stonewall's problem was that, after winning the battle for gay marriage, the organisation had run out of things to do. It wanted to keep its funding, so it pivoted to become a single issue group campaigning on gender ideology. The organisation was in effect taken over by a group of heterosexual men, mostly white and middle class, who wanted to say that they were women, and in effect Stonewall has become a men's rights pressure group, seeking to turn the clock back on the rights of women and gay people. When the CEO of Stonewall says that lesbians who refuse to have sex with men are "sexual racists", this is a good sign that something has gone wrong. Stonewall is now facing a funding crisis, as many of the public sector and corporate bodies which it had ideologically captured have dropped out of its lucrative endorsement schemes, and the Bailey case and the Cass Review haven't done Stonewall much good in PR terms.
Some decades ago, Bulimia was not widely known until someone wrote a paper about it. Soon afterwards, large numbers of teenage girls were claiming to be bulimic. In more recent times, there were almost no cases of teenage girls claiming to be boys, but now such cases are numerous, for reasons which are obviously to do with social contagion, coupled with the resurgence of misogyny fuelled by pornography, Andrew Tate, and Jordan Peterson.
It appears that, shortly before the election, Rosie Duffield, Jess Philips, and some other Labour women, and maybe also Wes Streeting (who is a gay man) took Keir Starmer on one side and told him to stop pretending to believe that humans can change sex. Starmer, ever the electoral realist, appreciated that he'd better do so. As the saying goes: "If you want my X, respect my sex".
In the US, Walz has recently vanished from the campaign trail. He has fallen a long way down the gender rabbit hole, from which Harris is trying to climb out, realising that women are fed up of men taking over their physical and political spaces. It is to be hoped that enough women will be motivated to oppose Trump on the grounds of reproductive rights for Harris to win. If not, we may all be in for a rough time.

I am a Y13 student who is currently doing an EPQ on the conflict between the manifestation of religious freedom and LGBT discrimination law, and very much struggling to find decent books on this topic.
So far, I have looked at some judgements (Lee v Ashers, Eweida and Forstater). However, we are expected to have a variety of sources for the project, including books. I initially decided on Gender, Sexuality and Law (by Ashford and Maine), but am reconsidering after having read some rather scathing reviews of it online. The other one I have looked at is Gender Recognition and the Law (by Flora Renz). I am yet to commit to either book, and have yet to find other books on the topic.
I am finding it difficult to separate the books that offer a legal perspective as opposed to a social or political commentary, and was wondering if anyone had any book recommendations/advice?

Another thing that may be of interest is the Charity Commission's recent damning report on the activist group Mermaids, which played a part in the Tavistock scandal.
You may also wish to be aware of the several law suits current in the USA which raise issues about gender and sex. These fall into three main groups.
One group involves States seeking to legislate against the medicalisation of children, which in the US is done by for-profit medical businesses, and Constitutional arguments about this.
Another group involves people who were medically transitioned when young who are now suing doctors for taking the medicalisation route and not advising the patient of the lifelong adverse consequences of that route.
Another group involves women in prison suing State governments which allow men who claim to identify as women, including men convicted of rape, to be housed in women's prisons, and women athletes suing the governing bodies of sports for allowing men who claim to identify as women to compete in women's sports.
In Australia, Tickle v Giggle is heading to the apex Court, and meanwhile some State legislatures have erased women as a legal class by Statute (it is notable that most of the legislators voting for such measures are men), and this is politically contentious.
Back in the UK, the financial future of the Green Party is uncertain because it is losing case after case brought against it by members of the party who have been treated unlawfully for expressing sex-realist opinions. Similar cases have been won or are in progress against various regulators, professional bodies, local authorities, the NHS, and the civil service.

One thing to be wary of is that the life cycle of a big deal litigation and the time taken to bring in statute is quite long relative to general perception of the state of play with social issues. Simply put, case law takes years to come about. Statute takes even longer. Books on the subject will take longer still. The zeitgeist is instant.
Memories are so short as to how long some of these social issues have been about. The trans agenda has only been where it is for less than 5 years - prior to that almost nobody took it seriously as a social issue. Same-sex marriage has only been around for 10 years. That gives a very short amount of time for big cases to happen, go through litigation, go to appeal at higher courts and become interesting. Then for them to be cited as good authority and then written about. As SB says above a lot of the popular writing isn't legal writing at all, they're just activist writing using law as a figleaf.
My advice to you would be to look at the landmark cases. The ones that are continually cited and used as good authority. Then read up and really really understand a few of those cases and the writing of experienced jurists, rather than read nonsense books written by people for whom the law is an inconvenience rather than a principle.
My go to would be family law rather than the Equality Act. I just don't think EqA cases (which are usually ET cases) are very interesting. Normally they're just a finding of whether or not someone was treated unfairly at work and there isn't very much to do with that information. I would start with something like Corbett v Corbett. There is plenty of writing on it, but I would guide you to Stephen Gilmore.
On your original point, I am a little concerned that this might all be a little too wide and difficult for an EPQ unless all you are going to do is a literature review. I think it might be a better idea to pick one particular question and explore it rather than try and take in a very large open ended idea. I think a legal history of same sex marriage wouldn't be the worst thing in the world, or maybe a comparison in the law between gay marriage in different jurisdictions, although be careful that you understand what the normal matrimonial law actually is in those jurisdictions in the first place. For an EPQ anything that you can produce a table of differences on and then work out your commentary on that from would be a good start. You'd get a similar start on something like ages of consent / marriage for straight vs gay couples.

@nwar
Not exactly in the scope of what you wanted, and probably a few steps to far for an EPQ, but a deep dive into Roe v Wade is like driving on the autobahn without a seatbelt. The facts of the case are not like anyone thinks they are and utterly repulsive to most people on the quote-unquote liberal-progressive side of things. In fact, the entire history of the abortion debate in the US is so bizarre as to leave anyone who has looked into it wondering how it got to the place where it is now.
If you decide to read Roe v Wade, all I can say is - get ready.

You may find this guide helpful for further reading: https://ks.echr.coe.int/documents/d/echr-ks/guide_lgbti_rights_eng
It draws together many of the ECtHR's leading authorities on LGBTI rights. It is very well structured and gives you a great overview of the current position of the ECHR. It was published very recently, so it will be very up-to-date. Make sure you understand the relationship between ECtHR judgments and the UK legal systems if you intend to draw on them.
If you wish to look further still, under public international law (treaties, etc.), these will usually be referred to as SOGI rights (Sexual Orientation and Gender Identity) - using that terminology may make researching a bit easier.

@nwar
Not exactly in the scope of what you wanted, and probably a few steps to far for an EPQ, but a deep dive into Roe v Wade is like driving on the autobahn without a seatbelt. The facts of the case are not like anyone thinks they are and utterly repulsive to most people on the quote-unquote liberal-progressive side of things. In fact, the entire history of the abortion debate in the US is so bizarre as to leave anyone who has looked into it wondering how it got to the place where it is now.
If you decide to read Roe v Wade, all I can say is - get ready.

I must admit that I find the Tavistock case very confusing. I know the initial ruling was overturned, but then the NHS itself issued a temporary ban which did end up being legally challenged, but the High Court upheld the ban - but the government introduced the ban after Tavistock won the case Bell brought against them (albeit on appeal)? I may have got many (if not most) of these details wrong, but this is my understanding of it so far.
Reading Mr Fraser's report on Mermaids was also a bit confusing regarding the Cass Review. Considering it was carried out by an independent party, Dr Cass, who did not have any experience working in gender identity services, has it assumed a sort of quasi-legal status? It seems to be given weighting to in a lot of the recent rulings - is this something that usually happens in law?

Ruth Bader Ginsberg correctly pointed out that Roe v Wade was incorrectly argued on the wrong part of the 14th Amendment. RBG, who at the time of the case was the leading sex discrimination lawyer practising at the Bar of the Supreme Court, would have argued a different case. As a Judge, she predicted that Roe v Wade was vulnerable on legal grounds, regardless of partisan politics.
RBG made a mistake, however. Obama pleaded with her to retire, so that he could appoint a forty year old replacement of her, but she stayed on, and died not long after her legal opponent but great opera-buddy Antonin Scalia. Trump's luck in getting three SC appointments was extraordinary. The time bombs he laid by appointing utterly unfit candidates to the Federal first instance bench are mostly yet to go off (although Diane Cannon has already exploded). Clarence Thomas and Samuel Alito appear to be immortal, curse them.

Gosh, I've never felt apprehensive (or this curious) about reading a judgment before.