Here's a list of a few different cookbooks and diet books I recommend. I'm somewhat partial to the paleo diet and high protein in general because I find myself to be drawn to carbohydrates and used to fall into a bad pattern when I would eat over a certain level of them.
30 Day intro to the Paleo Diet
The Caveman Feast
Great Paleo Cookbook
I haven't tried a gluten free diet myself because I do still keep more processed foods that have gluten in them than the paleo diet would dictate, but if you're looking for a quality gluten free guide that's great for both diabetics and those with Celiac's disease this book has a great set of dishes with a low glycemic index.
Here's a basic gluten free book
And here's a cookbook full of delicious desserts for those of us with a sweet tooth.
A gluten free dessert cookbook