I read "The Gap" series, a five-novel saga from Stephen R. Donaldson.
I think Donaldson does better with SF than fantasy. The series is set in a future as created by something called the Gap Drive, an FTL travel method that sometimes drives people mad. It starts out with a complicated little minuet of a story involving the lives of three people who live on the fringes of space (the first novel), but over time the series becomes a complicated tale involving a terrible cold war between an alien race (the Amnion) and humanity, the dangers of human greed, and one man's attempt to make the universe safe for humans. It's based very loosely on -- or perhaps sort of inspired by -- Wagner's Ring Cycle. (What's up with SF based on the Ring Cycle? I know of one video game that's a SF take on it, and there's a Captain Harlock anime series based on it...)
Anyhoo, I was told once regarding the Covenant the Unbeliever series that that if you can get past the rape scene in the first book, you're good. I think this is more literally more true of this series. If you can tolerate the (much nastier) rape scenes (that's multiple rape scenes, by the way) in the first book, you should be fine.
I dunno what's up with Donaldson and rape, but the important thing is you'll know you'll be able to handle the series overall if you can take the first book, in particular if you can have a certain amount of sympathy, no matter how small and how overwhelmed by hatred and disgust, for a mass-murderer and rapist, as he transforms from villain to victim. If you're capable of viewing a very, very bad person as a human being worthy of a tiny drop of sympathy, even if you can't forgive him for what he did (and the text makes it clear you shouldn't), then you'll enjoy the first book, and what follows it.
The first book is probably the best; while making it clear you should hate Angus Thermopile (the aforementioned rapist and mass murderer) for the things he's done, Donaldson deftly manages to make him seem human, which is vital as things totally fall apart for him, because otherwise you won't care when things go pear-shaped for him. The book starts with a listing of events as people understood them on a particular space station, followed by what REALLY happened.
The second book is also very personal, following what happens to the various characters after the first book, and completing various transformations: While Thermopile went from villain to victim in the first book, in the second book someone who seemed a hero becomes a villain, and the victim transforms into a heroine of sorts.
After that, the style of the books change, becoming less personal, even giving the occasional encyclopedia-like "supplemental data" entries on the universe, sort of like a reverse RPG sourcebook -- mostly fiction, with a little source material. However, this drawing back makes everything more epic, giving even more room for people to show themselves at heroes and villains. The last three books are a little overlong, but they keep you hooked.
What makes the series work is that while it is highly nasty and gritty, despite the cynicism of all the characters and the compromises they make, by the end of the series humanity is better off than it was at the start of the series, and there's been redemption -- or damnation -- for all the major characters. This including several characters that don't even get introduced until the second or third book, but turn out to be very important, especially in terms of how they intersect with the three main characters of the first book. (Of those "later" characters, I particularly like Hashi. Watch for him.)