Great Lisp primer!
This book is really great.
The author focuses on showing how to actually get things done in a practical way instead of just enumerating language features. After reading this book, you will feel like you have actually learned how to write Lisp programs.
Also, one great thing about this book is that it describes the condition system in its full power (one thing that is not so common in other Lisp books). Instead of showing how to do the same thing you would do with Java exceptions, Seibel shows you how to do better using Lisp. The chapters on object orientation are also very interesting, showing details of CLOS, the Common Lisp Object System (which is amazingly flexible and powerful).
I would definetely buy this book if I was about to start learning Lisp, but it only covers the basics. You will need other books later. More specifically, you will need books on advanced techniques and a reference for the language (which this book is not).