I want to read more but don't have any moneyWatch
Worth keeping an eye on Gumtree and Facebook marketplace, folk give away bags/boxes of books all the time.
However, if you want to read university level books, they can be extremely expensive. But since you want to learn, you can easily get older editions for much less on Amazon. Most newer editions have the same content as the old one, the only difference is that the questions and exercises are rearranged and changed, and prettier/colour pictures added to be able to charge students with ridiculous sums of money. I would prefer a hardcopy of a book so that I don't strain my eyes and can easily read them without my computer lagging.
pdfdrive.com and archive.org have some university level books if they are too expensive for you.
Another though look at joining your library online if you have not as they often have ebooks to lend out or otherwise you can always use internet archive library (just google) - limited leading time but you can borrow more then once