They at Paperback Library were particularly fond of conflating the original sort of Gothic fiction with post-Dark Shadows "supermarket gothics"...
Recycled for one of DC's short-lived gothic comics...
But PL wasn't alone...the first Award edition explicitly labeled this as a gothic...cover by Jeff Jones.
And if gothic readers were disappointed, as they were, by a fairly standard suspense novel...
...imagine what the innocent gothic fan made of "Carmilla"...
A Weird Tales serial, in boards from Arkham House, that *might* just fit if you squint at it the right way...
For some good reading on the subject, including the repackaging of other sorts of suspense and horror books to sell them to the Phyllis Whitney-style gothic audience, please see this excerpt from Joanna Russ's essay "Somebody's Trying to Kill Me and I Think It's My Husband: The Modern Gothic" as collected in Russ's To Write Like a Woman.
The Vault of Evil post that inspired this one...