Interesting: thanks I didn't know about Open Library.
Just joined up, and I see that E_ADEPT_DATABASE error on the first book I tried to download, exactly as you say.
Also fails in Sony Reader (even less clear about why than ADE).
Clearly an Open Library issue as scisslehannd22 says: and almost certainly not at all Adobe's problem other than the obscure error message.
Maybe it will start working again soon ???? (though already quite a long downtime since your first post about it)
I do think that ADE is a pretty poor program with terrible support.
I'm sure you will find the quality and support for Photoshop in a different league (as is the price!).