A solid effort! It's never easy to adapt an H. P Lovecraft story for cinema or TV. His narratives and characters were always rather unconventional and unpredictable. "The Dunwich Horror" is no exception but this 1969 effort is worth seeing.
Sandra Dee being considered too old for her role, I find an unfair comment. She was only 27 at the time of production and still looked pretty youthful! Dean Stockwell has the right quirky, offbeat quality for his role of Wilbur Whateley, even if he overdoes it on occasion. If it hadn't been him, I can imagine someone like Bruce Dern, Anthony Perkins or Donald Sutherland being cast.
Character actors Ed Begley Sr, Lloyd Bochner and Sam Jaffe are on hand to give the film a bit of class and some gravitas. Sadly, Ed Begley Sr passed away three months after the film was released. A fine actor was lost.
Being a typically low budget affair, the climax where the said horror is finally unleashed on the town was bound to be technically limited. "A. I. P" was never going to provide the necessary expenditure, in producing half convincing special effects.
The film has a pretty good narrative on the whole, although a few changes had to be made from the Lovecraft story. Given that Wilbur Whateley is killed about half-way, that wouldn't have worked for the film. It works well enough that he succeeds in stealing the Necronomicon book from the Arkham library, rather than being murdered by the ancient horror.
It is imaginative how the sets are created, especially the one representing the Whateley household. It gives off an eerie vibe!
I don't particularly care for all the irritating flash photography and the rush of colours. Audiences from the times may have tolerated it but I find it artificial.
I reckon "The Dunwich Horror" would have benefitted from being set during the 1920s - as when H. P Lovecraft wrote the original story. However, I can overlook that minor quibble.