[sam_on_the_web]

Most of the books it recommended were extremely popular titles (Girl with the Dragon Tattoo, the Martian, etc) and so out of the first 5 recommendations I got, I had already read 4 of them. This would be a lot more useful with a larger catalog.

[MikeBVaughn]

I think there's a bit of overfitting in the output. If you put in a book in the middle of a series, it will sometimes recommend the predecessor.