"Cinema's pretty cool, I guess" - Andrei Tarkovsky, probably
The original Maniac stands out when placed alongside the many, many other slasher films released around the same time in that it's primarily focused on the killer's perspective. This remake takes that idea a step further and quite literally places the audience in his shoes, with it being primarily presented in first person. And it's done to great effect, as the film presents audiences with a clear grasp of how he perceives and understands the world (especially the ways in which they are coloured by his misogyny and Oedipus complex), making for a deeply disorienting and unsettling experience.
More darkly funny than it is particularly scary, with James Whale having injected the film with a terrific level of razor-sharp wit. This, some innovative special effects which still remain impressive and an impish but menacing Claude Rains performance have allowed this to stand the test of time wonderfully.