5)Thud! by Terry Pratchett. I must admit that I'm completely new to Discworld, so this one's liable to change as I read the other books. That said, this is the only time I've ever actually gone "Aww" at a book, and the only time I've gone "Aww" at anything involving children (you know which bit I mean.), so props to Pterry for achieving that much.
4)Lamb: The Gospel According to Biff, Christ's Childhood Pal, by Christopher Moore. Funny, thoughtful, and contains the phrase "blessed are the dumbfucks."
3)Harry Potter and the Half Blood Prince, by J.K. Rowling. I've noticed that a lot of people have sort of turned on this series recently, but I still think it holds up well, and HBP is definitely the high point as far as I'm concerned. And regardless of whether I can still enjoy it all these years later, the Harry Potter series is what convinced me to try my hand at writing, which in turn made me realize that I was pretty damn good at it, and what's more, that I enjoyed it.
2)Hearts in Atlantis, by Stephen King. On closing the book, I quite literally did not know where I was for a few seconds. Tight plot, relatable characters, brilliant social commentary, and just generally entertaining.
1)Life, the Universe, and Everything- Douglas Adams is far and away my favorite author, and LUE contains my absolute favorite passage in the trilogy- the description of Bistromathics. Also the last Hitchhiker book to involve Zaphod, who is awesome.