If you liked Takeshi Kovacs, you really have to check out Iain M Banks, particularily Consider Phlebeas, even if he has gone rubbish lately. Ken Macleod also, ironically Newton’s Wake’s far from his best but it’s quite Kovacs-ey. (his Fall Revolution series is superb)
Dark fantasy- Must read George RR Martin and China Mieville. Mieville’s not yet been as good as he could be I think but still what he’s done is pretty damn good.
And just deviating a wee bit from what you said you actually want, but Kim Stanley Robinson’s Mars series is stunning. And Heinlein’s The Moon is a Harsh Mistress should be compulsory reading.
Here I’ve deleted a load of criticism, but, to cut it short Joe Abercrombie’s hugely entertaining but also a bit of an obvious hack, and recycles ideas and characters depressingly often. Oh look, another world-weary northern barbarian. Still, worth the read.
Alastair Reynolds has ideas, but IMO lacks craft and timing, in ways I can’t explain without dropping enormous spoilers- but after about 10 bazillion pages Absolution Gap ends the series (perhaps) with as much grace as a kick to the balls, despite having spent at least 2 bazillion of those pages having absolutely nothing happen at all. It is absolutely awful. Also, making space battles so dull is a gift. Wait. Time passes. I’m sure it’s more realistic than most but it’s still like watching paint dry, such a shame. And he’s not very good at post-human characters, as soon as he starts fleshing them out they become regular-humans with funny hats on. Still, for all that, for the sheer scope and imagination I think it’s well worth the visit, I just wish he had some discipline, or an editor that could keep up. His novella Galactic North is a real highlight (though does tie in with the abovementioned absolutely awful ending)