On-Sale date from the Direct Currents page of From Beyond the Unknown (DC, 1969 series) #8.
This cover mimics the Paperback Library Gothic series that was popular at the time, including the oval over a gold background and rendering the series name in the font Cooper Black. Perform an internet image search for "Dark Shadows Marilyn Ross" to see a comparison.
Set in 1840.
Father John and Rabbi Samuel appeared next in Sinister House of Secret Love, The (DC, 1971 series) #2 (December 1971-January 1972)