It's a small (parallel) world

 Here's something I found in a Goodwill store this morning: the goth romance Treveryan by Angela du Maurier. Angela was the sister of novelist Daphne du Maurier, who wrote Jamaica Inn, Don't Look Now and Rebecca.

The latter served as one of the inspirations for the first "parallel time" story in Dark Shadows, with Angelique standing in for the novel's title character. And, in the back of this edition of Treveryan, are ads for some of the early Dark Shadows novels by Marilyn Ross. After the television show added vampires, werewolves and other assorted monsters, Dark Shadows' appeal expanded into the youth market. But it's clear that Dan Curtis Productions and ABC originally thought their primary audience were fans of bodice rippers and the pulpier romance stories.