I'm having the same problem. It seems to be wide spread. People all over the net are reporting it yet nobody at Apple or anywhere else seem to even understand it. I have an iPad Air 2, latest o/s, latest updates to apps. I've got plenty of space. I've hard booted my iPad, reinstalled apps, and re-downloaded the file. It says "downloaded" but nothing else. No cloud icon or open icon. I have a total of 15 different books showing downloaded but won't open. Getting really frustrated, I need these books for a class.