I'm actually quite delighted to hear that BK was given the willies by SARDONICUS back in the day. I vividly remember my first time seeing it because of those very willies.
I think I first read about it in Famous Monsters, and I found the movie tie-in paperback and was suitably creeped out by reading it. Then it finally came to town and my dad dropped me off at the Gateway Theater in Fort Lauderdale (my avatar on the HTF) one fine Saturday morning, and I was loving every minute of it, till the graveyard scene freaked me out -- and when the Moment of Reveal came, I must have gone through the roof.
But I loved the story, and I've always thought it a fine Castle. Did he do any other Gothic horror? I don't think so. But the cast, the Von Dexter score, the mood, it all adds up for me. And it's a Halloween favorite around here. Friends and I watch it almost every year, and I'm delighted to hear we'll be doing so through the miracles of our friend Mr. Blu-ray this year.
Herewith, my paperback. I keep it in a small plastic bag -- not so much to protect the cover, but because this one is so brittle that it's been coming apart in sections over the years. But these are hard to come by, and I treasure the fact that it's the one I bought in '61.