story identification - Old Sci-Fi Novel where man uses horn to enter another world, learns he is a "god" of sorts?

I read this one in the very early 1980s, but I believe the story is much older – 50’s or 60’s. It’s very “pulp novel” in its themes and style – lots of action and adventure, little in the way of complex relationships or hard science. To use a film analogy, it’s more “popcorn movie” than art house cinema. I believe this was the first in a series of novels, but I’m not entirely sure about that point. Here’s what I can remember:

● The protagonist - an old man - discovers a horn inside a house. I’m not sure how he came by the horn, or if he lived in the house or was thinking about buying it. When he plays the horn a certain way, he accidentally opens a portal to another universe. The man, whose life is pretty miserable (nagging wife, health issues, and I think perhaps even some legal troubles) soon enters the portal.

● Once there, he discovers a tropical beach paradise. Everyone is healthy, young, and beautiful, natural food is superabundant, and the world has a “fountain of youth” effect on the old man. He begins to grow younger, gradually regaining his hair, his teeth, and so on. In a few days, he is restored to his physical peak.

● Eventually, the man learns that he is not who he thought he was. He learns he is part of a family or race of people that create pocket universes as their own personal playthings and rule them as god-like beings (albeit mortal ones). The laws of science and physics in these worlds function at the whim of the creator. Thus, in the tropical world, people do not age or get sick, being effectively immortal short of accident or violence. The man further learns he is not only one of these creators, but this world was his own creation.

● I can’t remember how the man came to Earth originally, but I think it was some sort of accident or mishap. Perhaps a form of banishment by other creators. The people who create these universes are depicted as often cruel and vain, a bit like Greek gods. The protagonist was himself very much like that, but his time on Earth as the person he thought he was has changed his nature to one more aligned with compassion and benevolence.

● The only other point that I can remember is, that there is a massive, infinitely tall mountain/spire in the center of the world. The man and I believe some companions climb this spire/mountain for several days in order to reach his fortress or kingdom above the tropical paradise. It may even be another world (not sure about that).

Any insight would be welcome!

Answer

The Maker of Universes, a 1965 novel by Philip José Farmer, first book in his World of Tiers series. Maybe one of these covers will ring a bell. Here is the Wikipedia plot summary:

The story follows Robert Wolff, a man disenchanted with his life and his marriage. One day, while looking at a new house, Wolff discovers a strange horn in the basement. Blowing the horn, Wolff is transported to a strange new world, the World of Tiers. Wolff finds himself initially in an edenic paradise known as Okeanos. This region is the first level of the planet, which contains a number of tiers like a wedding cake, separated by vast mountain ranges. The entire planet is ruled over by a cruel and mysterious lord named Jadawin, who created it. Okeanos consists of a beach, an ocean, and a small forest and is populated by nymph like humans who originated in and near ancient Greece. In this new world, Wolff regains his youth and vigor and falls in love with a local woman named Chryseis who lived in Troy at the time of the Trojan War.

When Chryseis is kidnapped, Wolff follows after her, climbing to the next level of the world, Amerind, a plains region populated by Native Americans and centaurs. Along the way he is joined by the adventurer Kickaha, who had also come from Earth, where he was known as Paul Janus Finnegan, some time ago. The two continue their adventure as they ascend the various levels of the World of Tiers including the medieval Dracheland and the jungle Atlantis. When they finally make it to the palace of Jadawin they make a shocking discovery; Robert Wolff is Lord Jadawin, who lost his memory after being defeated by another lord, and ended up stranded on Earth. At the end, Wolff/Jadawin is reunited with Chryseis and restored to his rightful place as ruler of the World of Tiers, his experiences as a human on Earth having tempered his previous cruelty.