I read a book in a library stack that was either a short book or a short story in pulp sci fi compilation book.
It starts by telling the reader that the planet was taken over by aliens and now ruled with watch towers. The people are monitored with fly patrols, curfews, and forbidden areas. A priest or men of religious power now help the aliens in the watch towers and one priest has a rebellious daughter. She is spoiled and tired of her sheltered mundane life so she escapes to the forbidden wilderness. Before night fall she has fallen into trouble and is on the brink of death when she is rescued by a wildman.
After the wildman saves the girl they rush back to his underground home just in time to miss the night patrols of the watchers. She is a snob but slowly comes to realize her situation. They then run because of the risk of being discovered.
Along the way they navigate down a river and passes through towns where they befriend a werewolf and meet an old steamboat captain/ringmaster of a freak show that they join. They realize a legendary Vampire Witch is after them.
Surprising twist ending. Amazingly weird but well told story. I'm thinking it was a 70's paperback but could be reprint of old 50's pulp.