On the blood types thing -- first heard about this about 15 years ago, when a colleague (I was working in a health food shop), looked at me, proclaimed "You're blood type AB, right? That's why you like such and such food." Only I had never told her my blood type; she just figure it out from my physique.
All the stuff I read about it, what each type looks like and what regime is healthiest for them, tends to hold true... I know a few exceptions, though. One friend is blood type A and he is very big boned, solidly built, a terrific meat eater, very physical, not dainty at all the way As are supposed to be. DH & his mom are O-, and they're sort of delicate & skinny (look like a type A or maybe AB). I don't know what book I read recently (probably the one others mentioned), but it did seem to have some crazy ideas in it, though. Something about how surgery should be done different for each type? Anyway, the original women who talked to me about it said that your parents' types can have an effect. I'm not sure that in the end it's all the helpful to know what one's type is and what that means you should or shouldn't eat; I think we can figure out for ourselves what a healthy diet is and what we foods don't agree with us. As AB, I'm supposed to be sensitive to both the A and B-type culprit foods (ie, soya, cow's milk, wheat, maize). And yet, I'm not really sensitive to anything -- except strong cheese sometimes makes me break out in a sweat, and in pregnancy I seem to go lactose intolerant.