I admit, I haven't read the book, but from my understanding of Agile methods and CMM, the two are not mutually exclusive. CMM is about improving and maturing the processes that you use. A company at CMM 1 has virtually no process, and can't repeat their results. But agile methods such as XP are processes, and often have even more effort put into improving them than more traditional methods such as the waterfall model. One common misconception about CMM is that it's about creating a whole lot of unnecessary documentation. If the documentation is unnecessary, that's not CMM at all, a CMM 5 company only does documentation that adds value to their processes, just like agile methods.