The book is a good overview on how to create game levels using a typical 3D application. It covers planning a level, creating meshes, some texture creation, and how normal maps, specular maps and other highlights work with existing technology.
However, the book isn't an even effort. The mesh creation concepts are the most informative, since they walk you through concept to final product. The same is done with textures, but if you own Luke's other book this is just a repeat and waste of space. If you want to create terrain, trees, and brush, the book points you to ... software to create them. Well, it's nice to know that things like this exist, but what if you wanted to actually create these on your own?
UV mapping is largely ignored, mentioned only in passing. You have the model and the texture, now what? If you want to know an efficient way to map your complex model to the texture, you're completely on your own.
If you know nothing at all, this book is a great start, granted you can find your own UV map tutorial to patch up your knowledge. Intermediate users will only learn a couple of things, and advanced users will waste their time.