One book says pinto beans are good for type O, another says type O should avoid. The cookbook is full of recipes with pinto beans for type O. What should I do?

Look at Typebase for pinto beans to find the latest rating for the Blood Type diet.
http://www.dadamo.com/typebase4/depictor5.pl?312

Look in the Genotype book for the rating for that diet.

Read your individualized SWAMI printout for the rating if following that plan.

If Pinto bean is an avoid for you, substitute a compliant bean in those recipes.  For most recipes, the taste will be close and the consistency will be fine.

I recommend using black beans instead.  

Finding out your secretor status will help you determine if pintos are acceptable, but I serve black beans to my type O friends since they seem to do better with them (& I do not have to know their secretor status)

Info on secretor status:

http://www.dadamo.com/knowbase/newbie/a.htm

I do well on pinto beans, but I second C_sharp's recommendation of black beans.  However they might turn a rice & beans casserole into an unappetizing grey color.  Adzuki beans (if you can find them) are excellent.  I also do well with black-eyed peas.  Good luck!