From the review:

The Definitive Guide to Symfony (which we'll call "the symfony book" from here on out) is an Open Source book written as a companion to the symfony PHP framework. Written by two of the most prominent names in the symfony community, Francois Zaninotto and Fabien Potencier, the symfony book is serves as not only a wealth of information for symfony developers, but also the de facto symfony manual.

Aaron talks about the contents of the book (introductory material, details on the "core architecture" of the framework, etc) and some of his thoughts on the book - good overall, but had a few minor issues that he had in reading it.