Once there's a pdf or other ebook available it'll be pirated. How that doesn't damage sales I'll never understand.
The Lazarus (object pascal ide) book is only available in a physical book format for this reason.
http://www.themillions.com/2010/01/confessions-of-a-book-pir...
In another life I wrote technical books, which at the time were only available in physical formats. That didn't stop electronic versions of the more popular books from appearing on usenet.
Because the people downloading it are not necessarily the same people who'd have bought it otherwise.
Plus exposure. I pirate a lot of stuff. At the same time I buy more books and music than anyone else I know.