Hard sci-fi inspired by Bob Lazar's real claims about S-4 and Element 115. An industrial designer gets pulled into a black site program to reverse-engineer a recovered craft. He has 72 hours before the signal reaches its origin point.
Free for 5 days, no catch.
→ https://www.amazon.com/dp/B0GF1KXMQK
Full trilogy is out if you get hooked.
Most alien invasion stories give them motivations that are basically human, resources, territory, curiosity, fear. Which works narratively but sidesteps the actually interesting question, right? An intelligence that evolved under completely different conditions wouldn't necessarily want anything recognizable.
Solaris is the obvious one. The thing isn't hostile or friendly, doesn't seem to register humans as significant. That's genuinely unsettling in a way that "they want our water" never is.
Color Out of Space works for similar reasons, no goals you can map, no logic you can follow.
Von Neumann probe stuff gets close sometimes. A self-replicating system running on a directive so old the original civilization might not even exist anymore, no emperor, no fleet, no message.
What are the best examples you've read?