This is such an interesting concept and because of technology, it's true now more than ever that authors can build businesses around their books. (muffin.wow-womenonwriting.com)
You need to build buzz around your book that will drive people into stores to seek it out. (pagetwostrategies.com)
They're integrated with existing social media, they have nice interfaces, they allow a community to build around a book. (bookmachine.org)