Interesting idea. I mainly read philosophy, classics, and some fiction. Anyway, I think between Goodreads and Amazon reviews, I can generally get a feel of what to expect. They also have the advantage because independent review/recommender systems are the norm, and they work for most people. I think reviews and recommendations are tough to get in to when you have a huge chicken/egg problem. Even if you aggregated all reviews for a book and added something unique on top, it's only making the experience marginally better.

I do think having unique context could be pretty interesting. The narrower and more specific a list, the more value it would add. Having a "My Top 5 Books" list provides no value to me. A recommender algorithm will win at that game. However, having a "Romantic Thrillers Where Protagonist Gets Kidnapped While On Vacation" list is at least something unique. I think search could be kind of addictive if there were tons of random and extremely narrow lists. If you did go this route it seems collaborating to build the lists would be pretty cool. Having lists tied to a user seems like it would make it harder to come up with really unique and narrow lists as a community. Maybe you could have both?