I haven't used emusic.com in a while, but they have a great music discovery model without necessarily having the most comprehensive library, built on the idea that they're a 'music magazine.' For numerous genres and subgenres and certain key bands/artists they would have an in-depth editorial attached to a dozen or so editors' picks (for an individual band it might be their influences and who they've influenced, other bands out of their scene, etc), and then other users' playlists, reviews, and people-who-liked-so-and-so-liked-such-and-such layered on top of it all.
I could see a similar 'magazine' model working for e-books, certainly for genre e-books, and it would put English majors to work
You get the run of the site and great reviews/criticism, plus 1-5 e-book downloads per month, based on subscription level.