The one possible pitfall of making a cerebral horror movie is that it is possible to think yourself right out of being scared. The best horror films get inside your head, but they get there through your gut, preying on your instincts and subconscious fears. The transformation scenes in The Thing may not say anything deeper than "Holy shit, a monster!" but they don't need to. When you're tied to a couch, watching someone's head split open and mutate into a toothy maw, the "holy shit" reaction is the only one that matters.
It Follows could have used some more gut shots, figuratively if not literally. It is immaculately plotted, acted, and shot. It's sober, evocative, and suspenseful. It is thematically weighty in a way that most genre films—even many non-genre films—are not. It also is not terribly scary, at least not in that gut-level, give-me-nightmares-if-I-think-about-it-before-bed sense. After a couple of great setpieces in its first half, the film settles into a slow-burn groove, which soon becomes a rut. Its pervasive, plodding dread matches the monster's unhurried implacability but is not engaging as horror. By the final act, one can sense It Follows screaming in second gear, unable to evolve or develop in a way that will allow the film to shift into a higher register for the climax. It follows, then it ends. Ho hum.
There is a lot to like here. After this film and his debut, The Myth of the American Sleepover, David Robert Mitchell has established himself as a director to watch. His control over the formal elements of his films is impressive, and he's mastered the skill (so rare these days among screenwriters) of gracefully developing his characters without relying on clunky expository dialogue. But if there's one thing that It Follows is missing, it's a Rob Bottin to work his hair-raising magic.