There is one first-time free paleo book today:

The Paleo Lunch For The Working Woman Easy And Delicious Paleo 
Recipes Volume 1 by Jessica Andrew
http://www.amazon.com/dp/B00A46DS0Y

This is the second in this series to go free. I reviewed the first 
and found that all the recipes were taken from the web. I will write 
a similar review for this in a couple hours. Since it is free, you 
may still want to have the recipes conveniently in a Kindle book form.

These are free again today:

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

How To Lose Weight Bundle (6 Books: Juice Fasting, Paleo Diet, Raw 
Foods Diet, and More!) [Includes Richard Nikoley's book]
http://www.amazon.com/dp/B007AXQOIW

Tasty Paleo Smoothie Recipes: 21 delicious, healthy and easy to 
prepare smoothies. Suitable for special diets including Paleo, 
gluten-free and dairy-free (Tasty Paleo Recipes) by Elisabeth Peters
http://www.amazon.com/dp/B008DYK65O