Google's Play Books service launched last year as a competent reading app, and a necessary pillar for Google Play. But one feature readers have since been asking for is the ability to incorporate their own files into the library, and now Google is adding that option to the service.
Play Books supports PDF and EPUB files, which can be uploaded through the online library on your desktop. The feature appears to still be rolling out, so don't worry if you get a 404 right now. For comparison, Amazon's Kindle service has long supported uploaded content, but it relies on awkward email attachments.