Hive

Before you get into the horror bits you are presented a realistic relationship that is falling apart. Then when you do get into the crazy and weird stuff later it keeps it grounded and relatable for most. This makes it easy to recommend even for non-horror fans.

And those horror bits are really nuts and are never fully explained, which in this case is to its advantage. It is a mix of psychological and body horror, and good old slashers.

I found it be the perfect length: nothing is wasted and there is no filler trying to pointlessly make it longer for the sake of it. The characters are great, the horror is great, the plot is great, it is just great.