Every mod is broke down into a few sections and is aided by multiple pictures. Though all black and white, you won't miss a detail. The Nintendo section has a brief history of the company, but oddly, they are the only ones to gets this special treatment. Each chapter finishes with various web links that can provide more information.
And that's the book's biggest flaw. Everything included here is available for free on the web if you look in the right places. Granted, you won't find all of this in one place, but it is there. The system roster is also a bit weak, missing more modern stuff like the Gamecube and older systems like the Genesis. The Genesis has a wonderful S-video mod that is nowhere to be found and the Gamecube can be tweaked to play imports.
In the end, Syngress has published a wonderful 600-page book written by some of the best. Regardless of what era of gaming is your interest, this book probably has you covered. Even if you've never touched a soldering iron, "Game Console Hacking" will get you there.