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.
Functional programming/paradigm. It's a pretty nice language to learn it (my intention was to learn Clojure, but I read this book first so that I had an small base).
The cool thing about learning in Lisp (or Scheme) is that the language doesn't really get in the way. It's less about learning the syntax of a language and more about focusing on the algorithms/concepts.
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.