There are two first-time free paleo books today:

This first one has been around for a year. Lots of reviews. It isn't 
much of a book:

The Paleo Solution or Wheat Belly? A quick comparison between two 
books on eating paleo with a wheat-and-gluten-free diet (99-CENT 
REVIEWS) by Michael Anderson
http://www.amazon.com/dp/B0064ARDAU

Paleo Lifestyle Magazine Interviews - Issue #2 - September 2012 by 
Paleo Lifestyle Magazine
http://www.amazon.com/dp/B0095XMN8K

This author stuck paleo in as a tag. This is becoming more common. 
Author's want their books to appear in as many searches as possible. 
And Amazon allows this. I checked it. It is not at all paleo. I will 
write a review.

No Fail Fat Loss by B Flatt
http://www.amazon.com/dp/B00A4HQE5Y

These were also free in the past:

30 Paleo Diet Recipes Breakfast, Dinner, Snacks, Desserts by Riley Monroe
http://www.amazon.com/dp/B0096PPHQC

The Paleo Aficionado Dinner Recipe Cookbook (The Paleo Diet Meal 
Recipe Cookbooks) by Amanda Matthew
http://www.amazon.com/dp/B009AIWNV2