I upload all my ebooks to Google Drive, and only have a few in my Google Play Books library at any one time.
Play Books lets you read online from a browser on any device without downloading the book, and saves place between devices, so it is far and away the best choice for me. You can also add epubs straight from your Drive, so you don't have to download then upload something to add it to your library. I like its read aloud function as well. It's organizational abilities are really lacking, though, so I don't keep everything I own in there, just what I'm currently reading or may read in the near future.
@mortcs Please contact Amazon support, as they are the ones who can push the full book to you. We have already e-mailed asking them to push it to all customers who bought the book, but as an individual customer you might be able to get a more timely response by contacting them yourself.
@Chaos-master Ah I see. Unfortunately there is no Premium option for manga. I think, iirc, the issue is Premium's are DRM free and the Japanese manga publishers didn't agree to allow that. I'm not sure if this is being worked on for the future or if it's just how it is. I don't follow manga so it's all I know, someone else may be able to expand.
Yup, the Japanese Publishers aren't currently (as far as has been revealed to the forum, at any rate) willing to allow DRM-free manga, so there aren't going to be Premium Editions for manga unless that happens.
More the likely need to logout/log back in. That's what happened in my case. It doesn't specifically tell you when your login times out, just stops working. Go to Account, then click the log out button.