It's also possible that he has created science fiction with a focus on post - apocalyptic Earth. In these stories, survivors are trying to rebuild society from the ruins, while dealing with new threats such as mutated creatures or the remnants of a failed technological experiment.
Maybe he has written some stories centered around time travel. For instance, a character might go back in time to change a crucial event in history, only to find that it has unforeseen and complex consequences that ripple through time and space. His works could be full of such mind - bending concepts.
I'm not sure specifically which works Gary Garrison has. But generally, his science fiction might include novels about space exploration. These could involve a crew on a mission to a distant star system and the various obstacles they encounter along the way, like asteroid fields or malfunctioning technology.