The author says he was motivated to write Wolf of Shadows after receiving many responses from children to his adult novel about nuclear war, Warday (1984). Many of the children asked "What will happen to the animals?"

His first published novel, The Wolfen (1978), reveals his interest in wolves.

Strictly speaking, it is a horror novel, but it contains thought-provoking comparisons between the wolf and human societies. It is about a group of werewolves who have evolved to a nearhuman level of intelligence, and who live in hiding in the Bronx, where human beings serve as their main prey.