Many of us have assumed, a priori, that electronic books substitute for print books. While I don't have controlled, quantitative data to refute the proposition, I do have plenty of experience with this stuff, and all that experience leads me to believe that giving away my books is selling the hell out of them.Link
More importantly, the free e-book skeptics have no evidence to offer in support of their position -- just hand-waving and dark muttering about a mythological future when book-lovers give up their printed books for electronic book-readers (as opposed to the much more plausible future where book lovers go on buying their fetish objects and carry books around on their electronic devices).
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.