Philip José Farmer is a prolific science fiction writer whose success is based on his deft mixture of three primary components, "religion, sex, and violence," in each of his many works, according to Franz Rottensteiner in Science-Fiction Studies. In addition, he is often credited with introducing the first mature depiction of human-alien sexual encounters into the genre with his 1961 book, The Lovers. Although Farmer is sometimes dismissed as a writer of formula fiction whose least successful works are written "hastily, sometimes downright sloppily," as reviewer Leslie A. Fiedler once charged in the Los Angeles Times, his admirers find Farmer's exploration of timeless themes within an action-oriented adventure plot a winning combination. Furthermore, "the number, richness, and complexity of Farmer's series," according to Thomas L. Wymer in the Dictionary of Literary Biography, "can lay claim to uniqueness."

Farmer's "Riverworld" series, which Roland Green of Booklist called "one of...