The Joy of Clojure
Also available on amazon.com.
If you've seen how dozens of lines of Java or Ruby can dissolve into just a few lines of Clojure, you'll know why the authors of this book call it a "joyful language." Clojure is a dialect of Lisp that runs on the JVM. It combines the nice features of a scripting language with the powerful features of a production environment—features like persistent data structures and clean multithreading that you'll need for industrial-strength application development.