When I updated from 4.5.6 to 4.5.7, suddenly my entire library disappeared, including all the bookshelves (including All Books, Purchased, Borrowed, etc.). When I double-click on an epub file, it opens ADE but does not display anything. When I add a new bookshelf, it shows as Untitled Bookshelf 1, but the title above shows All Items. When I add another, it shows Untitled Bookshelf 2, but the title shows Not Read ... If I keep going, the titles above all the Untitled bookshelves show all the missing default bookshelves. However, none of the bookshelves is populated with the books that were there before upgrading.
Once I've added back the bookshelves, I can add the books to the shelves from the My Digital Editions directory. I can then open the books to read them. However, if I exit ADE and restart it, all my shelves are gone again!
Just to add one more thing. When I restart ADE and it is empty. If I repeat the process of adding back my bookshelves and trying to add the books back to the library, I get an error stating that the book is already in the library. This makes me suspect that my library is still there, but the disappearing bookshelves are preventing me from accessing the books. Before restarting, when the book I had added back to the shelf was there, I could open it and read it. Now I cannot access the book at all because it is in my library but invisible due to the lack of bookshelves. Not only can I not read it, but now I cannot return it to the library to check out more other books either. Even if I try to check out a new book, the book never appears due to the missing shelves.
I'm completely stuck without any books!