A review by torts
Eat Right 4 Your Type: The Individualized Diet Solution to Staying Healthy, Living Longer & Achieving Your Ideal Weight by Catherine Whitney, Peter J. D'Adamo

Did not finish book.
I mostly just read the introduction and the chapter on my blood type. But from what I did read, I got a pretty strong impression of the type of advice that was being dispensed.

Basically, it's like vaguely-racist astrology. The ideas behind the advice were mostly sound. (Including suggestions to eat more of certain fruits and vegetables, and to avoid others, with reference to pseudo-scientific reasoning for how these foods affect the bodies of certain blood types and thereby affect the way they feel. Even if people don't follow the advice, getting these recommendations surely helps get them thinking more about their food choices and how those choices make them feel.) But if it "works" for you, it's probably because it was generically good advice, not because it tapped into some magical science behind the random accidents of how you were born.