Saw this at Amazon, thought you would find it interesting

Product Description
This book is the best guide you can have for SAVING MONEY on car rentals anywhere in the world. It is in a simple and easy to read format that talks candidly about the subject of renting cars and the secrets to saving money, along with avoiding countless headaches in the process…. More >>

How to Save Big Money on Car Rentals: Uncovering the Secrets They Don’t Want You to Know