I would suggest the library, too
I've not read the book, but the only references I've found didn't place much faith in the concept. There may well be some good diet tips in the book, you never know! BOB has incorporated some of the ideas with her SB plan and is happy with the results. Whether or not that actually has to do with blood type may be questionable.
The Mayo Clinic says there is no evidence to support the claims in this book. Harvard Medical School also says the same thing.
There are a lot of diets out there which are based on specific ideas, but most have no scientific basis. The diets may work, but it's because they require that we restrict our food intake (consume fewer calories). Eliminating certain foods, however, may not always be a good idea because we risk developing a nutrient deficiency.
From another point of view... The idea that our bodies digest foods differently based on our blood type just doesn't seem logical. I really think that our bodies were designed to be more efficient than that.