There are about a half a dozen ways that you can examine this unusual Swedish silent classic, and I'm going to give you a once-over so you can determine if it's the sort of film you want to watch or not.
Experiment in narrative. Häxan isn't structured quite like any other film you've ever seen. It begins with a shot of the filmmaker, Benjamin Christensen, looking stern, and proclaiming that he created the film over the course of two years. Christensen then launches into what is essentially a university lecture on medieval cosmology, complete with pointer stick and citations. Then Christensen begins to weave skits about the Inquisition into his tale, occasionally dropping back out to present more lecture material, concluding with a short story about modern times. At a couple of points, Christensen even tells us what the actresses in the skits told him while they were playing the scenes! It's an unusual mix of documentary and drama, and I can't tell if it was totally revolutionary or if modern cinematic storytelling conventions hadn't quite set in yet. In a way, the combination of a straight-talking (and slightly sarcastic) narrator with a "re-enactment" makes Häxan the ancestor of both the horror anthology and such TV docudramas as Unsolved Mysteries.
Exploitation film. From the first time a witch pulls apart a stack of hay to reveal a severed hand, it's clear that Christensen is prepared to put on a spectacle using the best technology he could get, and the film is a bonanza both of early special effects (mechanical dioramas, stop-motion, double-exposures, bizarre costumes) and lurid subject matters (demonic dances, nuns gone mad, torture devices demonstrated, and blatant masturbation references). It brings to mind later exploitation films that used education as an excuse to get away with showing such sinful matters as sex, drugs, and gore.
Gender perspectives. All the characters who are afflicted with devil visits or mental illness are women. All the demons, the inquisitors, and the physicians are men. Häxan is part of the medieval tradition of associating women with chaos and men with order, but displays the worst of both traits; women driven mad by their unchecked emotions are confronted with the hideous and merciless bureaucracy of the Inquisition. (However, there's a short scene with a woman pilot at the end - I wonder if that means anything?)
Mental health. Despite Christensen's "we're men of science now" demeanor, it's clear that he isn't totally sold on his era's view of mental illness. He treats the sufferers as innocent waifs and the organizations that are supposed to help them as short-sighted and mean.
The Great War. Christensen began filming this the year after World War I ended. German filmmakers had already used insanity and mind control as a very effective metaphor for the war in 1919's "The Cabinet of Dr. Caligari," and Christensen revisits those themes here, even including a reference to the war in the modern skit. In earlier times such a horrific event would've been blamed on the devil, Christensen seems to say, but as men of science, we've proved that he doesn't exist… or does he?
Link to a free version of the film is right here, and feel free to comment or email me if you want to talk more about it.