Arguably the one horror writer of distinction to get a raw deal at the movie is HP Lovecraft. Okay, his stuff is densely worded and chock-full of his own concocted mythology, which is harder to explain than the usual 'Oh, so it's a werewolf eating the villagers.' But it's still a pity that so few efforts to put HPL's ideas on screen stand up to more than one watching.
Among the best is - perhaps surprisingly - a Roger Corman flick that he made during his Poe period. The Haunted Palace is in fact touted as 'based on a poem by Edgar Allan Poe and a story by HP Lovecraft'. This is such a blatant lie that the magnitude is almost admirable. The script by Charles Beaumont is a free but respectful adaptation of The Case of Charles Dexter Ward. The Poe bit consists of Vincent Price's voice-over quoting a few lines from 'The Haunted Palace' that aren't even especially apt.
What the story loses in the transposition to film it gains in cinematic virtues. Vincent Price plays Ward and his evil ancestor Joseph Curwen the New England 'wizard'. Ward's long-suffering wife is the cracking Debra Paget. Lon Chaney is excellent, if somewhat under-used, as the long-lived henchperson. And there's a thing in a pit, and another thing in an attic, plus curses and a mob with torches. The sets (it's an all-studio job) are good, too, especially the village of Arkham - much smaller than Lovecraft envisaged, but still adequately ghoul-haunted. Highly recommended, this one - a neglected, unpretentious minor masterpiece.