Aside from Edgar Allan Poe (and possibly Richard Matheson), no writer has had their short stories adapted into horror films more often than H.P. Lovecraft. Lovecraft has been so influential to the genre that even films which are not direct retellings of his stories, like Sam Raimi’s The Evil Dead series, are based around one of his inventions, the Necronomicon, or the Book of the Dead. One of the first appearances of the Necronomicon on the big screen was director Daniel Haller’s 1970 creep-fest The Dunwich Horror.
The Dunwich Horror starts at Miskatonic University in Massachusetts with Dr. Henry Armitage (Ed Begley from 12 Angry Men) giving a lecture about the legendary Necronomicon, a one-of-a-kind book about witchcraft and the occult. After the lesson, Armitage entrusts one of his students, a young woman named Nancy Wagner (Gidget’s Sandra Dee), to return the priceless volume to the school library. 
While putting it into its secure glass case, Nancy is approached by a young man who introduces himself as Wilbur Whateley (Dean Stockwell from “Quantum Leap”) and asks to see the book. While Nancy initially says no, she is soon hypnotized by Wilbur’s gaze and lets him walk off with the book. Just as Wilbur begins to look through the Necronomicon, he is stopped by Armitage, who takes the book back but is charmed by Wilbur enough himself to go to dinner to discuss the book, Wilbur’s family and their home town of Dunwich. After repeatedly asking to borrow the Necronomicon (and repeatedly being denied by Armitage), Wilbur misses his bus back to Dunwich and Nancy offers to drive him. Wilbur lives in a big spooky house in Dunwich with his old grandfather Whateley (Sam Jaffe from The Day the Earth Stood Still) and a mysterious locked door that appears to be hiding something menacing from the world. While at the house, Wilbur drugs Nancy and, after a night of crazy dreams and visions, she is convinced to stay there with him. Meanwhile, Armitage does a little research about the Whateley family and discovers that Wilbur’s mother, who currently lives in a mental hospital, gave birth to twins and that Wilbur’s brother was born dead, although no one ever saw the body. Knowing something is wrong with Wilbur, Armitage has to try to save Nancy from him before she gets too deeply involved, but uncovers more horrible secrets about Wilbur, his family and his reasons for wanting the Necronomicon.
The Dunwich Horror is a fun hybrid horror movie. It was executive produced by both Roger Corman (Little Shop of Horrors) and Samuel Z. Arkoff (The Abominable Dr. Phibes), giving it a spotless B-movie pedigree and, even though the script takes a few liberties with Lovecraft’s original story, it is a surreal mix of a supernatural occult thriller and an alien monster movie. Because it was adapted from a short story and expanded into a feature length movie (by L.A. Confidential screenwriter Curtis Hanson and Lock Up scribe Henry Rosenbaum), the story does drag a bit in places, but the plot moves in a way that makes sense towards a classic B-movie climax, and the characters, although stereotypical, are well written enough to carry the scenes in which action is light.
A recent graduate of the Roger Corman Film School (the name given to the group of successful filmmakers who all worked with Corman early on in their careers), Daniel Haller had already directed one Lovecraft adaptation (Die, Monster, Die!) for Arkoff, so he was familiar with the mood and style of the writer’s work. 
Before he was given a chance to direct, Haller served as the art director for Corman’s spooky Edgar Allan Poe films, and his eye for detail carried over nicely into The Dunwich Horror. The look and feel of the film is very much like a classic Hammer horror film, with light and dark working together in an almost gothic way. The Necronomicon in the film is a much more realistic representation of the book than in later incarnations, but it still emanates the musty, dusty look of evil for which it has become known. The little details that Haller painstakingly creates help to give The Dunwich Horror an underlying air of eeriness.
Although the production design for the film may look like Hammer or Universal, the visual effects are pure Corman. The emotions of shock and fear are shown onscreen as electronic color blasts added in post-production, turning the images negative and coating them in primary colors like red or blue. 
The monster in the film is also noticeably low-budget, although Haller gets around this limitation by only showing the creature in quick little bursts of editing. Finally, Nancy’s dream sequences are shot with what looks like amateur actors through Vaseline-coated lenses and cloth filters to give the impression of unrealism. As a student of Corman, Haller learned all the tricks of a low-budget master filmmaker.
H.P. Lovecraft’s stories have been made into movies as much as any fantasy/horror writers, with differing results depending on who is behind the camera. The Dunwich Horror, however flawed it is in places, is still an important film in horror history, if only because of Lovecraft’s name and the presence of the infamous Necronomicon.