Sorry to inform you, but I and many others think bloodtype diet is a scam and fraud.
It was popular in the ninties and 2000 for some reason. And the the author is a good seller and has earned a hell of lot cash as the book has sold millons. But his moral is soso..
He make a lot of claims that this and this is science and evidence but all in all everything is a joke and bullshit.
I have to admit I was excited of these theories in my youth and for some time ate as it said. Now I know better. Dont trust everyone.
For diet look into Mediterranean diet, The new nordic diet, etc.. you can find a lot of info on internet today about what is considered the best diets based on summarized research science.