This is going to sound strange, but I've been reading some damned fine Harry Potter fan fiction recently. It's a work in progress called Harry Potter and the Methods of Rationality. I picked it up on the recommendation of the recently-deceased hacker genius Aaron Swartz, who had this to say:
This is a book whose title still makes me laugh and yet it may just turn out to be one of the greatest books ever written. The writing is shockingly good, the plotting is some of the best in all of literature, and the stories are simply pure genius. I fear this book may never get the accolades it deserves, because it’s too hard to look past the silly name and publishing model, but I hope you, dear reader, are wiser than that! A must-read.
As it says at the beginning, you really need to give it a couple chapters to get started before passing judgment — the first bunch are quite silly and it doesn’t seem worth sticking with until you’ve gotten past them.It's really funny and really thought-provoking. Very highly recommended. Best of all, it's available in ebook form for free!