He spans genres such as science fiction, horror and fantasy, sometimes within the same novel.
Simmons' novel
Summer Of Night recounts the childhood of a group of pre-teens who band together in the 1960's to defeat a centuries-old evil that terrorizes their hometown, Elm Haven, Illinois. This novel is similar to Stephen King's It,in its focus on small town life, the corruption of innocence, the return of an ancient evil, and the responsibility for others that emerges with the transition from youth to adulthood. Soon after this novel, Simmons, who had written mostly horror fiction, began writing science fiction. He is a respected author of these and other genres, including the mystery and the thriller.
In January, 2004, it was announced that the screenplay he wrote for his novels
Olympos would be made into a film by Digital Domain and Barnet Bain Films, with Simmons acting as executive producer.
Ilium is described as an "epic tale that spans 5,000 years and sweeps across the entire solar system, including themes and characters from Homer's "The Iliad" and Shakespeare's "The Tempest." In July, 2004, Ilium received a Locus Award for best science fiction novel of 2003.