The Answer Is in Your Bloodtype by Joseph Christiano, Steven M. Weissberg (1999, Paperback, Revised)

This book has a unique viewpoint on health, claiming that one's bloodtype affects just about everything about a person's life. For instance, the author claims that your bloodtype affects your life span, love and compatibility in your relationships with others, your likely illness profile, as well as what foods your body will assimilate and function best on for maximum health. Very interesting reading, and the subject is covered quite thoroughly. The book even includes 7-day menus for each bloodtype, as well as grocery lists of "very beneficial foods" for each bloodtype.