There are many, many books that I've really liked. I loved the Harry Potter saga and, the Darth Bane trilogy, reading both sets multiple times. As for my single favorite book though, it would probably be Soul Music by Terry Pratchett. A great parody of the history of Rock N' Roll as seen through the filter of The Discworld and, one of the books in the Death story arc
(Death being my favorite arc) Perhaps the best thing though is the image it leaves us with:
hm...thought I could find a better pic than that but it's not bad...