There are a few big differences between a book like this and fitocracy or a thread on this forum, aside from the fact that one is a money-making scheme.
1) The book ends. Fitocracy and the forum members will be here to support you through your endeavor as long as you're willing to stick with it. There's still some missing pieces of the puzzle, but they at least provide a solid base to help keep you on track and motivated. Whatever it is they offer, however, the big thing is they don't dead end when you're most vulnerable to relapse.
2) Communities provide several serious benefits that a book alone cannot. Vicarious reinforcement and helping relationships are both well recognized resources for inciting cognitive and behavioral change.
It's like saying, don't get in a romance unless you have a good counselor, because when it fails, (and they easily fail, romances) you are going to think love is just another word for pain. It's like thinking that someone who failed a year of study and had to repeat it will be forever damned.
This is a weak metaphor, but I would liken it to someone falling in love with a celebrity they don't actually know or a sex worker. It's not the general case that I'm trying to discourage (by all means, people can and do succeed without having a personal trainer to guide them), but in this particular instance I strongly believe it is going to end very, very badly.
Changes you say. Why should be becoming a muscled version of you better than have a belly and give that time to improve your chess skills or your piano playing, or draw a webcomic?
Aside from the fact that this forum and his book are aimed at people trying to make these changes, the changes are of particular importance in that they will improve the general quality of life in countless ways (ease and safety of every day activities, self-efficacy, reduced anxiety, reduced depression) as well as prolonging it (drastically reduced chance of cardiovascular disease, coronary artery disease in particular, reduced chance of hypertension, diabetes mellitus, stroke, osteoporosis, certain cancers, etc). I became a personal trainer after I made the transformation myself and I'm passionate about helping others make it.
Neglecting your health is frighteningly common and I've seen first hand both the consequences of doing so and the rewards of turning things around. There's a reason I'm back on these forums daily trying to help anyone I can for free. My only agenda is helping people who want to make these changes. Bradshaw's agenda is to make money.
Put your trust where you will, but understand that I have a reason for being as harsh as I was.