This is a science fiction book I read in high school, circa 1986 or 1987, it had already been around since maybe the 50’s or 60’s? It’s about an astronaut or maybe an explorer who I think is stranded or left on an alien planet that he is meant to explore or get ready for humans? He stumbles in to a residence and is grateful because he’s close to death, but quickly discovers everything there is not fit for humans so he really isn’t saved like he hoped. He persists. Time goes by. He uses his knowledge and training to adapt the environment to his human needs. He starts to thrive. He’s accomplishing his mission. He gets ready to contact his group. He discovers a mirror. He looks in to it. He’s no longer human. His environment and its systems didn’t adapt to his needs, he adapted to it. WHAT IS THE NAME OF THIS BOOK?
Maybe Enchanted Village, by A.E. Van Vogt? Despite the name, it is science fiction, and it’s a short story.
It’s been a long time since I read it, but maybe ‘Judgement on Janus’ by Andre Norton. I seem to remember that the person who was left on the planet slowly developed into an alien compatible with the planet’s eco system.
Dark They Were and Golden Eyed, by Ray Bradbury?