I'm not sure it should really count as a "Lisp book", but The Art of the Metaobject Protocol" is one of my favorite technical books ever.
It takes some knocks for not really containing anything about how to use CLOS. Instead, it's how CLOS is built. At a higher level, it's "how to build an object-oriented language/object system from scratch" using Lisp as a vehicle.
Richard P Gabriel was one of the six persons responsible for the CLOS specification: Daniel G. Bobrow, Linda G. DeMichiel, Richard P. Gabriel, Sonya E. Keene, Gregor Kiczales, and David A. Moon.
Richard was also the CEO and founder of Lucid, Inc. - a Common Lisp vendor. His company developed and sold a production quality Common Lisp implementation for various UNIX systems.
Further, I think it should be emphasized how much there is to CLOS. I've seen a number of CLOS tutorials that stop after showing how to do in CLOS what can be done in other OO languages, and don't really indicate how much more there is, let alone show how to do those things. Keene's book does go in to this. There are a few very minor differences between what she describes and what is in the final standard though.
I think the Keene book should be avoided by all means. I don't think it is a good introduction into OOP or CLOS. My recommendation would be Peter Seibels Practical Common Lisp.
It takes some knocks for not really containing anything about how to use CLOS. Instead, it's how CLOS is built. At a higher level, it's "how to build an object-oriented language/object system from scratch" using Lisp as a vehicle.