I found the following link:
http://literature-map.com/
You enter an author, and some computer will calculate, an' I quote:
"What else do readers of (author X) read?"
So if you like, for instance, Saul Bellow; the computer will say it's likely that you will also like the authors that are near to him in this graph:
I actually don't think it's very accurate, but maybe someone thinks it is. Plus, the archive of authors isn't very large. I hope it's helpful to someone ...