The Chronicles of Narnia, by C.S. Lewis

I read this entire series over and over again as a child and teenager.  I still have my original set of books and it's in sorry shape; they've been read so many times!  C.S. Lewis has a great talent for storytelling and building worlds and characters that seem real.  I always looked forward to losing myself in those stories.  It's hard to name a favorite among the books, but if I had to it probably would be a tie between The Magician's Nephew and The Last Battle.