There are seven first-time free paleo books today. Six are the 
Caveman Family Favorites series. The seventh is Paleo Lifestyle 
Magazine Interviews - Issue #3. There are also two that were free in 
the past (one is just low carb). You can see all of them here:

http://www.amazon.com/s/rh=n:283155,k:paleo,p_n_feature_browse-bin:618073011&sort=price

Be careful going down the list. Stop at the point when they are no 
longer free. Amazon will list ones that are "read free" for Prime 
users, so you have to check the second price, which has "to buy" after it.