I'm a huge fan of AudioScrobbler - it's just the niftiest bit of kit imaginable.
It's about to go through a rocky patch tho, because they've introduced moderation based on a rather limited model...
But, anyway, I'm thinking - what would an AudioScrobbler for books do? Presumably if you type in the ISDN number (a unique ID) you could bring up author and title. And from there, you'd have a 'slowscrobbling' system that would track your reading habits over time.
Anyway, follow up how my idea does on the AudioScrobbler fora.