There are four first-time-free paleo books:

35 Delicious Paleo Slow Cooker Recipes For Busy Families by Jena Staples
http://www.amazon.com/dp/B00CDVIU4W

The Healthy Paleo Smoothie Diet: 20 Recipes to 
Energize, Lose Weight and Feel Great by Rose Davidson
http://www.amazon.com/dp/B00C6NCWGE

Easy Paleo Breakfast - More than 30 Paleo Recipes 
to Start the Day off Right by Patricia Davis
http://www.amazon.com/dp/B00C8SN7ES

Was ist denn Paläo? - Seltsam, neue 
Steinzeit-Diät lässt die Pfunde wie verrückt 
purzeln! (German Edition) by Oliver Heimbold
http://www.amazon.com/dp/B00BUYFYQK

Then these three are not really paleo, but the 
authors have given them paleo tags to have them appear on a paleo search:

Cabbage Rolls - Golubtsi - Step-by-step Picture 
Cookbook How to Make Cabbage Rolls (Famous Ukrainian Recipes) by Oksana Vitruk
http://www.amazon.com/dp/B00BI2AK5O

Incredibly Delicious Soup Recipes from the 
Mediterranean Region (Healthy Cookbook Series) by Vesela Tabakova
http://www.amazon.com/dp/B00B7LBLW2

Belly Fat Blow-out!: Burn Fat, Lose Inches, 10 
Day Plan to Jump Start the New You (Get Fit - 
Especially for Women... by Stephanie Atwood M.A.
http://www.amazon.com/dp/B00CBLA33K

There are also a few others that were also free in the past. See:
http://www.amazon.com/s/rh=n:283155,k:paleo,p_n_feature_browse-bin:618073011&sort=price