World of Tiers

World of Tiers is a series of novels by Philip Jose Farmer.

Ancient Artifact: The Horn of Shambarimen.
Author Avatar: Paul Janus Finnegan (note the initials).
Cool Gate: Inter-dimensional machines/gates.
Dimensional Traveler: Paul Janus Finnegan (AKA Kikaha the Trickster) and Robert Wolff spend much of the novels traveling through artificially created universes.
Interdimensional Travel Device: People can travel between the artificial universes of the setting by using gates. Gates can be activated by various means, including tokens and playing music on a special horn.
Portal Cut: One of the many interdimensional teleport gates is a trap that dismembers by severing the connection and the intruder.
Portal Network
Red Pill B Lue Pill: An aging man with a failed life and a shrewish wife is in the basement of a tract house he is buying when a door between the worlds opens up. He can stay with his living-death retirement or leap into the utter unknown. Soul-killing safety vs death-or-glory.
Significant Monogram: Paul Janus Finnegan.
Villainous Incest: Incest is perfectly acceptable among the Lords and Ladies of the pocket.
World Shapes: The World of Tiers takes the form of a world-sized tower of Babel, just that the continent-sized layers (tiers) are way wider than they are tall. And the top layer has the Lord's palace on it.
Year Inside Hour Outside: Time in the pocket universes moves quite differently indeed.