What Space Fiction Novels Explore Isolation On Long Missions?

I keep thinking about this one recently – isolation in these stories isn't just a physical thing, it’s a total system failure of connection. The classic is obviously 'Solaris', where the planet itself is this incomprehensible consciousness that reflects human loneliness back in the most terrifying way. The scientists are together but utterly alone because they can’t communicate with the thing they’re studying. What gets me more lately are the quieter, weirder ones. Like in Adrian Tchaikovsky’s 'Children of Time', you have a human survivor literally alone for centuries on a ship, his only company an AI that’s degrading. His chapters are this brutal, slow-motion study of a mind unraveling because it has nothing familiar to latch onto. The AI can’t provide real empathy, it’s just a mirror. That’s scarier than any monster – your own mind, with too much time and silence. Then you have the social isolation in stuff like 'The Left Hand of Darkness'. Genly Ai is physically among people, but the cultural and biological gulf is so vast he’s perpetually the outsider, unable to truly trust or be understood. It’s a different flavor of lonely, one that makes you question whether any real connection across such divides is even possible.