Kropp achieved popular acclaim after the publication of his third and fourth novels One Hundred Times to China and Greencastle.

The story is a fantasy based on an old nautical legend about an island made of derelict ships floating in the Sargasso Sea.

centers around a mysterious woman who commits suicide in a mental hospital and the subsequent attempt of two young men to discover what part she played in their respective lives years earlier.

Kropp's 1979 opus, One Hundred Times to China was also published by Doubleday and became a staple of many American high schools' required reading lists.

This post-apocalyptic tale of a man trying to shepherd his wife and children to the safety of a secret mountain cabin resonates with Kropp's impeccably crafted tension and trademark gentleness, with a focus on humanity's better angels.

A lyrical coming-of-age story set in the early 1950s, Greencastle tells the tale of three boys who love mystery and science fiction.

He finds that in his small, conservative New Jersey town, he must face down bigotry, class-struggles, teen-age cruelty, and serious misunderstandings at the hands of his school teachers.

In 1975 he joined the English faculty at Southern Illinois University Edwardsville where he taught until he retired as a senior professor in 2002.

While at SIUE he taught a wide range of courses: fiction and poetry writing, The American Novel, Shakespeare, American Literature, Victorian Literature, Classical Mythology, Literary Criticism, Literary Editing, Egyptian Hieroglyphs, summer seminars in Creativity and Composition for high school teachers, and courses in music and writing for psychotic adolescents at the Alton Mental Health Clinic.

In 2007 Kropp lectured around the country, including at the Archon (convention) in Collinsville, Illinois where he gave a presentation on "Ancient Egypt: an Alien Mind."

His latest project is The Devil at Simon Episcopus, the story of a brutal murder at a conservative Christian college somewhere in the Midwest.