One of the criticisms I had of Dave Eberly's previous 3D Game Engine Design is that it didn't really say much about how to design an engine. Rather, it focused mostly on the programming/implementation details, which was disappointing to some. This new book is what many people expected from the older book.
In this book, the author walks through the design and architecture of a 3D game engine, using his Wild Magic engine as an example, but also drawing on his experience developing NDL's NetImmerse. Throughout, he describes why each design decision was made, and in many cases alternative solutions are discussed as well. This isn't just a high level discussion, however, as ample source code, figures, equations, and sample applications are included to get you started with implementation.
The topics covered include the core engine systems, scene graphs, renderers, cameras, LOD, animation, terrain, special effects, physics and collision detection. Numerous sample applications and tools are also included. Dave's writing style is clear and minimally conversational, and he's kept the math to a minimum, making this a remarkably easy read.
This isn't a complete treatment of a game engine, since some important topics (e.g. scripting, audio) aren't included, but the material it does cover is worth it. Whether you're currently working on a game engine, planning to start one, or just want to have a better understanding of how they work, you'll be happy with this book.