The Little Schemer is a very fun book! If you are thinking about learning Lisp, go for it. At least, give it a try. It's quite different from most books out there, but it's very good nonetheless. I read it last year while in the train and it's quite entertaining.
EDIT: I forgot to explain why it's such a good book: it teaches you how to think in Lisp. It doesn't focus at all in the syntax.