Sisters never carries any feeling that De Palma is showing off or flexing his cinematic chops because he can, or is above the material. The film is utterly transfixing because it plays its schlock straight, and paired with Hermann’s hair-raising throwback score, the effect is giddy.
The first full flowering of the De Palma style, the film cleverly uses split-screens and cross-cutting to string the audience along while heightening the emotions of any given scene nearly to the point of parody. The movie is playful and provocative -- at once one of the scariest and funniest horror movies of the '70s. [21 Oct 2018, p.E7]
At the time, its way of wringing thrills from genre conventions at the same time it mocked them seemed imaginative and original; but in the light of Carrie (1976), Obsession (1976), and The Fury (1978), it seems more like a dead end—the mark of a superficial stylist unable to take anything seriously, including his own work.
In retrospect, it does indeed appear as a highly efficient gut-ripper, with far more suggestion than De Palma's later work of the loose-end flux of real life going on in the background. There is, however, much early evidence of his rampant misogyny, his increasingly blatant stealings from Hitchcock, and most unforgivable of all, his clear distaste for the people he creates.