Extra stamp(s) on top page block, title page. Tight and almost square; spine is flat with 1 line down length.

The Maker of Universes - first in the "World of Tiers" series by Philip Jose Farmer. When Robert Wolff found a strange horn in an empty house, he held the key to a different universe. To blow that horn would open up a door through space-time and permit entry to a cosmos whose dimensions and laws were not those known by our starry galaxy. For that other universe was a place of tiers, world upon world piled upon each other like the landings of a sky-piercing mountain. The one who blew that horn would ascend those steps, from creation to creation, until he would come face to face with the being whose brain-child it was. But what if that maker of universes was a madman? Or an impostor? Or a super-criminal hiding from the wrath of his own superiors?

[For a better set-up and summary, here is a review by Lester del Rey]:
"These books deal with a decadent race who once mastered all science. Each Lord, as he calls himself, can now literally build himself a private universe - a pocket universe, as it is called - to his own design and with its own laws of physics. The first book shows us Robert Wolff being called into one of these universes - a world laid out something like a Babylonian ziggurat. The Lord had peopled it with all sorts of mythical beings, abducted from Earth or created. And now the Lord is missing, and the universe is going to hell in a hurry. Wolff and the mischievous Kickaha the Trickster set out to rescue damsels and restore order. It's a romp of adventure and marvelous inventions... The books are totally lacking in significance, relevance, or symbolism - and they are just pure fun to read. [-Lester del Rey (from Analog December 1977.)]