At a relatively late age, American writer Philip José Farmer won acclaim for his first science-fiction novella The Lovers (1952), which combined alien biology and sex. It worked so well that he has been working the same features into his novels and stories ever since. One of his noteworthy early stories was "Open to Me, My Sister", whose title gives an idea why it was considered "disgusting" by potential publishers.

Not that Farmer's tales all strike the same note. In fact, they include some of the most varied and exotic writing in sci-fi, sometimes crossing over into the fantasy realm. His Father Carmody series of stories in the 1950s features a murderous priest who sorts out theological puzzles on various planets. In his novel The Wind Whales of Ishmael (1971) the sole survivor of Herman Melville's Moby Dick falls through time into a future Earth when the oceans have dried up and primitive people have taken to the skies in airships powered by gas-filled animal bladders.

Between 1965 and 1977 he produced an imaginative and humorous series of novels known collectively as World of Tiers, which gained a following. The first in the series, Maker of Universes, begins with mild-mannered professor Robert Wolff walking through a wall into another universe. In a world of stacked environments he must fight his way through various levels to regain his rightful place as ruler (a life he had apparently forgotten during his stay on earth). The world-hopping fun continues in The Gates of Creation but Wolff's ally, the pleasure-loving trickster, Paul Janus Finnegan (also known as Kickaha) comes to steal the reader's interest—to take over as the central character in the rest of the series with A Private Cosmos, Behind the Walls of Terra and The Lavalite World. The series was revised and republished in the early 1980s.