This is a short science fiction book that also has a bit of fantasy. It’s the first in a series, but can be read as a standalone story.
Time for a light novel review here. This is a pretty famous property and I remember the anime was popular when it aired, and nowadays it still has a big fanbase. I never watched the anime, although I was always curious about it.
This is a book series (duology) that is not that famous (I think) but worth reading.