Duck Blood Soup is participating in Kindle Match Book. This means that if you buy the paperback version of the book, you are entitled to a free copy of the Kindle version.

Details from Amazon:

Introducing Kindle MatchBook
For thousands of qualifying books, your past, present, and future print-edition purchases now allow you to buy the Kindle edition forĀ $2.99, $1.99, $0.99, or free.
Look for Kindle MatchBook on print and Kindle book detail pages of qualifying titles. Buy the new print book first and then buy the Kindle book for $2.99 or less.