From the Amazon blurb:
>In part 1 of The Common Lisp Condition System, the author introduces the condition system using a bottom-up approach, constructing it piece by piece. He uses a storytelling approach to convey the foundation of the condition system, dynamically providing code to alter the behavior of an existing program. Later, in part 2, you’ll implement a full and complete ANSI-conformant condition system while examining and testing each piece of code that you write.