What law book should I read ?Watch
Letters to a Law Student, The Rule of Law and What About Law? are all good books for an insight into studying law and law itself. Try searching on Google for 'Law reading lists' as some unis publish lists of books they advise their students to read before starting their degree.
Hope this helps
Weird Cases by Gary Slapper is fun. If you have to be serious about it, a lot of people read Letters to a Law Student or The Law Machine. But I wouldn't.
I'd read some cases (there are plenty available at Bailii) since that's likely going to constitute the bulk of your course.
To add a bit of depth to your essays you could read A Very Short Introduction to Jurisprudence, which will likely be more than sufficient to add another level of argument to most first-year essays. I know an above poster said not to read jurisprudence but I guarantee he's not talking about that book, rather Hart, Dworkin, Kelsen etc (which I wouldn't recommend reading unless you've read philosophy before and enjoy it).
It's probably also worth doing a little bit of background research into the English legal system (i.e. the operation of statute and precedent, it's unlikely you'll need to know much detail) unless you've done A Level law.
Uh... other stuff which might be useful... a vague understanding of basic economics... the same for various moral philosophies (basically the sort of level to be able to recite shortly the difference between act and rule utilitarianism)... of course LtaLS is great for basic essay technique... you could read a wikipedia page on the differences between common and Civil law... the same for law and equity...
Finally, read Free Culture, it's ****ing GREAT.