I saw that you asked about paradise alien books. Honestly, I get a bit tired when people just recommend 'The Left Hand of Darkness' for every vaguely alien question—it's brilliant, but not exactly the 'paradise' vibe, you know? My absolute favorite for this niche is 'Semiosis' by Sue Burke. It's about colonists landing on a planet they think is utopian, only to find the plant life is sentient and has its own, very different, ideas about harmony. The tension comes from this beautiful, deadly ecosystem that feels like a paradise until it very much doesn't. The sci-fi is hard enough to feel plausible, and the alien intelligence is genuinely non-human, which is a thrill in itself.
Another one that hooked me was 'The Book of the Unnamed Midwife'—wait, no, that's dystopian, scratch that. I'm thinking of 'The Vanished Birds' by Simon Jimenez. It's more of a space opera, but there's a planet called the Canopy that's described in such lush, vivid detail it feels paradisiacal, yet it's central to a mysterious, galaxy-spanning conspiracy. The plot weaves time dilation and corporate intrigue into discovering what that 'paradise' really costs. It’s less about action thrills and more about a slow-burning, profound unease that builds into something huge.