Common LISP: The Language

In this greatly expanded second edition, six completely new chapters cover the Common Lisp Object System (CLOS), conditions, Pretty Printing, Loops, Series, and Generators. All of the new material -- well over half the book -- is clearly distinguished from the original text. It reflects changes or potential changes to the language resulting from some 185 votes of the ANSI committee on standardizing Common Lisp. It includes as well fresh examples and additional clarifications, warnings, and tips -- all presented with the author's customary vigor and wit.

This is the Lisp programmers' bible. If you need to know the official specification, every function defined in Common Lisp can be found in here somewhere. Anyone vaguely serious about programming in Lisp for extended periods of time should keep a copy of this book for reference. However, note that while this book is clearly written, it is not an introduction to programming in Lisp--Common Lisp: The Language only offers the language specification.