Go deeper into the categories. Amazon for example stops at Space Opera. But that's still a very large genre. Let users tell you what kind of features the specific space opera has. i.e. Alternate Reality? Space Battles? Technical Technology descriptions? You know REALLY research the book genres so that you can improve your recommendation system. Someone who likes light sci-fi will probably HATE technical sci-fi that spends 4 pages describing how a certain thing works.
Spend a few books to have nicer images made. I mean those 3 images really make the site look cheap.