two good books regarding kefir and the health  benefits of same, and how to 
make kefir easily with many substances other than  dairy:

wild fermentation - by sandor ellix katz

the body  ecology diet - by donna gates

these books do not promote neanderthin /  paleo styles and beliefs, but you 
will find some nice recipes and lots of  thought-provoking info and 
techniques that often compliment paleo-eating  standards.

---BONNY in Kentucky  (lurker here for many years, not  paleo yet tho!)