I won't add much to Roninspoon's writeup on this superb movie, except: The movie was directed by William Friedkin, his first film after The Exorcist.
The score is by Tangerine Dream, and contributes strongly to the otherworldly mood. Friedkin said that had he heard them earlier, he would have asked them instead of Mike Oldfield to score The Exorcist.
The DVD is from Universal Studios, catalog number 20420. Extra features are minimal: Bios of the cast and crew, and the theatrical trailer. Aspect ratio is the execrable 1.33:1, ie it's been pan & scanned. Film transfer is of acceptable quality but not excellent. Single layer DVD.
Nevertheless, this is one of the most gripping films I have ever seen. The squalor and horror that these men fled to (and among which the locals live their entire lives) is palpable, and the suspense is truly of white-knuckle intensity, and relentless. Well worth the money.