Behind the wall of sleep is based on a H.P. Lovecraft story, and though I haven't read a lot of Lovecraft I have seen a lot of movies based on his work. This little gem is certainly a must see for Lovecraft lovers. Not so much for it's closeness to the story, which I can't comment on, but for the simple quality of film.
Behind is about a psychiatrist in a low rent asylum who takes on an inbred patient who killed his family. Problems ultimately arise when the psychiatrist becomes obsessed with the patient believing that a deformity on the patients back is a deity who longs for freedom, and brains.
Though the acting is at times hard to watch, it is almost fitting in the melodramatic and Gothic settings. The cinematography is hectic and "artschool", but again works well with the story.
Don't get me wrong. This movie ain't perfect, but compared to many of the Lovecraft movies this is one of the more enjoyable. It won't kill you to watch it once so I say give it a try. But don't say I didn't warn you.