So when I was invited to try Riffle, I was a bit hesitant (do I really need another site to update?), but I gave it a shot anyway and I am SO GLAD that I did! Riffle is very image-based, so in a way I guess it's a lot like Pinterest, and it appears on the screen as a collage. To keep things organized, you can put books into lists and search by categories, and each genre has an editor that culls lists of books so you can keep up to date with new releases and old favorites. In addition, you can mark books as "read," "recommended," "interested in," and "currently reading." Then, you can follow users to see what they're reading, recommending, and view their lists.
It's a great interface, and so easy to use without demanding a lot of time or mental effort. And because it's linked to Facebook, you can easily set up an account and recommend books to friends!
Screen shot of what my Riffle account looks like:
If you want to try it out, click here for a special access code (the site is still in beta stage)! And I hope you find me and check out my lists!