I just finished the last Harry Potter book, and I really enjoyed it. I think it was the best of the whole series, and now I want to go back and read them all again. And also re-read The Hobbit, by J.R.R. Tolkien, which is my favorite fantasy book of all time.
My favorite non-fiction book is Hackers by Steven Levy. My favorite sci-fi book is Neuromancer by William Gibson, especially as part of the series. My favorite programming book is the C language by Kernigan and Ritchie.