This! Book! Is! So! Great! It came out at around the same time as Gone Girl so a lot of people were like, "if you liked Gone Girl you'll like this too" and that's true, but also false, because people who don't like Gone Girl will still like this, and people who have never heard of Gone Girl will like this too and I love it so much. 
 It's a noir-tinged contemporary psychological thriller in that genre of "somewhat unstable woman is married to The Worst Guy Ever and we cheer her on as she gets her revenge on him" but that's just like part one of like six separate parts. It's also very low key with lots of quiet moments but that just makes the suspense build even more because everyone's busy walking dogs and drinking coffee but you know it's all building to something TERRIBLE and then also the ending is all plot twisty while simultaneously vague, which is perfect. 
 Anyway, it's sad on so many levels that A.S.A. Harrison died without having time to write another novel, most selfishly because that means I can't binge read all of her other books. But if one were to write one novel, this is an excellent legacy to leave. Super recommend.