If you accept the alternate interpretation (spoils)
... that we were with her inside her head while she imagined a plot for her book, then it's pretty cool. Calvino-esque. Otherwise a subpar addition to the home invasion genre.
shareI actually feel the opposite. If it's all inside her head, feh. I don't need If on a winter's night a psychopath. Aside from one sequence, there isn't any narrative genre-bending, and then there are a handful of inverted tropes (such as the cat not dying). I would argue that something like Funny Games is more in line with what you're describing.
As a straight-ahead, take everything as real (aside from the obvious part where she imagines alternate scenarios), then I consider it an above-average entry in the home invasion genre.
Fortunately there seems to be enough for people to choose the interpretation of their liking.