Overdrive just released their top ten lists of the most requested ebooks and audiobooks (they do this every month). There are 8 lists, and they are divided by fiction & non, audio & e, and juvenile & adult. There's not a whole lot of change from January.
One thing I noticed today is that you can tell which publishers have a smart digital policy by comparing 2 related lists. Take, for example, the Juvenile Fiction lists, both audiobook and ebook. Stephanie Meyer has the same 4 titles on each list, and 3 of the tiles have been on the list for over 3 years (since publication, more or less). But if you look at Rick Riordan, you'll see that while he has 5 titles on the audiobook list, he has no titles on the ebook list. I'd say that that is a good sign that his publisher hasn't released hs novels as ebooks.