My all time favorite genre for every kind of fiction in existece was always dark fantasy, but it's hard to find content of said genre. When it comes to literature, I could only find The Broken Empire trilogy by Mark Lawrence (which I highly recommend, though I warn about it's raw and brutal nature) and The Black Company, by Glenn Cook, and The Blade Itself series, by Joe Abercrombie. I would like to receive dark fantasy book recommendations, I don't mind the brutality or cruelty it comes with it.
If you don't mind some SF aspects, the Coldfire Trilogy, by C.S. Friedman, was pretty good and dark as I recall.
The only one I have read so far was 'The prince of thorns'. I can't give an opinion of the book (I am thoroughly biased), but the writing skill was certainly fine and the characterisation well done.
Clive Barker writes Dark Fantasy/Horror. Check out his 'Book of Blood' it is a collection of his short stories, Some Dark Fantasy, some horror, and some a mixture of the two (though the line where dark fantasy becomes horror is debatable).
Any book set in the warhammer universe, the Witcher series, though not all of the books have been translated. Cannot think of anything else at the moment.
If you like The Black Company, you'll probably like Steven Erickson. Also: Warhammer/WH40K books. R. Scott Bakker Peter Brett Neil Gaiman Michael Moorcock Scott Lynch KJ Parker Caitlin R. Kiernan Mervyn Peake Brian Catling Etc. Also, you may want to distinguish between "dark" and "grimdark" because that'll change the authors on the list.
Pact is incredibly dark and is also a very original piece of writing. If you don't mind sci-fi, Blindsight is worth mentioning as well.