The emptor must caveat real well these days. While I think that the advent of e-readers has a lot of benefits (though I don’t currently plan to obtain one), any new technology signals that it has become popular and mainstream when it is invaded by crooks, garbage and advertising. (Okay, sorry, that was triply repetitive.) Anyway, do keep an eye out when buying, so you don’t get sucked into the Great Internet E-Trash Vortex of these sorts of books.
Over time, having moved from writing into editing, I have also seen this evolve. For example, I used to get tons of book review requests, but one day they just ground to a halt. What replaced them? Seriously irritating spam trying to bribe 5-star reviews out of people. I’ve had to change my whole guidance to editing clients with regard to marketing, because I once knew how to generate book reviews, and it no longer works.