I thought it quite good.
It's not a typical story, not something you've seen a million times (although it borrows from here and there more to provide red herrings than anything else). It is a VERY slow burn. It requires the audience to care enough about the couple to wait quite a long time for the payoff, so we have to enjoy just being with them. I thought the actors brought just enough to the table for that to work, but it won't for everyone.
Mostly though I credit it with being its own thing. These days anything that isn't paint-by-numbers genre work is welcome.