We were talking this afternoon, and I got asked "What is your favourite book?"
And while I was running through many thousands of possibilities, the supplementary question was "And what would you take to a desert island?"
I found the second question easier - I chose "The Feyman Lectures", a three volume set that would keep me busy for years improving my understanding of physics.
I found "favourite book" a lot harder to name, but eventually I went for "Lord of the Rings". I've read it twice, which is something I almost never do.