I have mixed feelings about this program, but I do love the free books. But sometimes I feel like I am drowning. To stop that feeling I use Ereaderiq. (There are other similar services)
1. Go to Amazon's webpage and search for the e-book you want.
2. Go to EreaderIQ and click on the Kindle Price drops tab
3. Enter your e-mail, and the ASIN or URL from step number one. ( Note: to get the book for free, you must enter the CURRENT price in the price drop field)
Oh, and I think this works for paper books as well as e-books.