Annihilation

Area X has been cut off from the rest of the continent for decades. Nature has reclaimed the last vestiges of human civilization. The twelfth expedition arrives expecting the unexpected, and Area X delivers. They discover a massive topographic anomaly and life-forms that surpass understanding. But it's the surprises that came across the border with them, and the secrets the expedition members are keeping from one another that change everything.

Synopsis from Open Library.