Annihilation: Book 1 by Jeff VanderMeer

Area X has been cut off from the rest of the continent for decades and nature has reclaimed the last vestiges of human civilisation. Expedition after expedition into Area X has failed to uncover its mysteries and the true nature of its danger to the world. Now a twelfth expedition makes the attempt, a group of four women: an anthropologist, a surveyor, a psychologist and the narrator, a biologist.

Their mission is to map the terrain, record all observations of their surroundings and of one another, and, above all, avoid being contaminated by Area X.
 
A harrowing cosmic mystery at the vanguard of eco-fiction, Annihilation has only become more pertinent to our reality ten years after its first publication.