This book is a high-level overview of agile and iterative development styles. It provides an overview of the reasons for agile development, giving the motivation for using these methods, and some contrasting and complementary descriptions of important examples.
The book is at its best in its descriptions and comparisons of four agile methods (Scrum, XP, Evo and RUP). The descriptions are in enough detail to give a good flavour of each one, and how they should (and should not) be applied - with extensive cross-references to each other. This both contrasts the strong and weak points of each method, and shows their similarity, which gives a good intuitive background of how agile methods work.
Although the book does not give enough information on the agile methods to allow the reader to start using them in anger, the book includes recommended further reading with each chapter.
I found the book somewhat evangelical - giving the impression that no waterfall-based project could possibly succeed (backed with large amounts of rather one-sided case study evidence). This grated at times. I would have liked to see more negative experiences on the agile side - not just on the waterfall side.
In summary, this is a readable book, which gives a good start point for anyone interested in agile methods. The main reservation that I have is based on its evangelical tone - the author's clear enthusiasm for iterative development seemed at times to overshadow his critical facilities.