There are many resources to learn Lisp, here are a few we recommend investigating:
- Practical Common Lisp
A popular book available for free. It assumes you already know programming. It gives a good coverage of the "core" of the language and goes to the point.
- COMMON LISP: A Gentle Introduction to Symbolic Computation
A book addressed to people new to programming.
- The Common Lisp Cookbook
A modern, community maintained resource covering many aspects of Common Lisp programming and beyond, from editor setup to style. The front page lists many other resources for learning, such as books (some available for free) and other web sites. If you already know another Lisp/Scheme, the cookbook can serve as a good crash course.