This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
It probably would be nice to know in which format(s) the ebook is available if known beforehand. With eink readers you still are limited to either Amazon or Epub (or remove DRM illegally, or root specific Android devices and run the Kindle app; both approaches are niché ... or illegal). And some publisher still think that PDF is an acceptable ebook format but that is a catastrophe on such devices. Maybe it is possible for the sponsors to provide that information as it could influence the choice of ebook or pbook.
With O'Reilly books you get 3 digital formats: ePub, Mobi, and PDF. I have several O'Reilly books, all sync 'd automatically to my Dropbox account, in all three formats, so I can read them anywhere on any device.
I believe if you get the print format, you can register the book and still get the three eBook formats as well, either for free or a small price.