Peter Seibel. Practical Common Lisp. Apress. ISBN 978-1-4302-0017-8. 2005.

The classic, very thorough and hands-on tutorial introduction that doesn’t skip the hard parts like the condition system and non-local blocks and exists (and the relationship between the two). It’s also got good chapters on CLOS.

The text is complemented by a set of modern examples, for web services, database, and binary file parsers: quite a long way removed from the examples in many introductory texts. It doesn’t make much use of macro programming in these examples, which is a shame, so follow with On Lisp or Let over Lambda once the structure of the language is clear.