If you're craving more sci-fi that nails that gritty, realistic feel of 'The Expanse', you're in luck. One title that immediately springs to mind is 'Revelation Space' by Alastair Reynolds. It's got that same blend of hard sci-fi and political intrigue, but with a darker, more cosmic horror twist. The world-building is insane—ancient alien artifacts, factions at each other's throats, and a sense of scale that makes humanity feel tiny.
Another deep cut I adore is 'The Three-Body Problem' by Liu Cixin. It starts slow, but once it grips you, it doesn’t let go. The way it explores first contact and the looming threat of annihilation is terrifyingly plausible. Plus, the sequel, 'The Dark Forest', takes the apocalypse theme to a whole new level with some mind-bending theories about cosmic sociology. If you loved the realism of 'The Expanse', these will feel like stepping into another meticulously crafted universe.