Just go to Gnooks, enter three authors you like and you get recommendations you may like too. In my case, already the first recommendation was head on and it was an author i read a lot from and i liked a lot.
But it also offered further recommendations. It works best when you use not too dissimilar authors, like
Interestingly, some of the authors were already suggested to me by others based on my praise of others. The site also offers the same service for movies and music. At least for movies (about music i am not capable of judging) the service gives similarly credible recommendations.
The collection of known authors is far from complete. E.g. I missed Daniel Suarez when i was looking for my favorite Science Fiction writers.