Amazon has quietly started a new program called Matchbook. If the publisher enrolls their books in the program, Amazon purchasers of print books can get an Kindle e-book version for a discount. The price for Matchbook must be between zero and $2.99. All of my books have been set at 99¢. This means if you have ever bought one of my print books on Amazon, you can now pick up a Kindle version for less than a dollar.
Here is a link that will display all of your eligible titles.
You'll see all the books you've purchased that are enrolled in this program, but I'm sure you'll jump on my books first. If not, then maybe second? Anyway it's a good program, especially for people who have made many purchases through the years, but have only recently acquired a Kindle.