When you sign up, you will have to supply a little bit of information about yourself. I did it and I didn’t consider any of the required questions to be probing too deep for my personal information. Of course one piece of information is your e-mail address. In the week since I’ve signed up, I’ve not gotten any e-mail from the sponsors or from Wowio except for my sign-up confirmation.
You can download as many as three books in a given day. What you receive is a high-quality PDF file with the full contents of the book. The first couple of pages of the book are ads for the company sponsoring your “purchase” of the book. They even personalize the first page with your name. I can only assume this is to discourage you from passing it to a friend. Given that the service is free, your friend can download their own copy.
None of the books I’ve received to date are truly designed as ebooks. You are simply receiving a PDF of the printed book. Still, you can get a wide variety of titles for free so it is a great way to check out some books that you might not normally order.