Another idea:

With downloading Metadata and/or covers in bulk, it would be good to have an option to cue them up first and go through them one by one so you can make sure the right details are being picked up.
So rather than going into each book, clicking the 'fetch metadata from server' button, choosing the info and going back to the book, and clicking next. I am suggesting you select the books you want to fetch metadata from the server for, it brings up the options for the first book, you choose the option you want, click next and it bring up the option for the next book.
Hope this make sense.