If you've gone looking for mid-list authors on a Nook or a Kindle, you probably won't find anything but their most recent work. (The last time I tried, neither the Kindle nor the Nook passed the Stanley Elkin Test.) Most e-book selection is wide but incredibly shallow. It appears that the upcoming Google Editions store could change that:
Although details about Google's forthcoming digital bookstore, Google Editions, are still hazy, at least we now know that it's going to have a huge number of books. Google has said that "nearly all" U.S. publishers will be included in the bookstore. Over 20,000 publishers and individual authors will be part of Editions, accounting for 2 million of the projected 4 million books on the site. The other 2 million books are older works that have fallen out of copyright and can now be offered by Google.
When you think of the acquisitions that Amazon has made for the Kindle, and when you look at the numbers that Google are already parading around, it's going to be awful hard for Apple to catch up with those two.