I think this is a “mystery suspense thriller.” It was masterfully written in term of plot development. Three female characters — Rachel, Anna, and Megan — told the story from their angles chronologically. Be careful to notice the date, since each told the story in her own time-line.
Rachel suffered alcohol induced amnesia (convenient for plot development). She had complicated and painful reasons to drink and lost so much from the drinking itself. Anna and Megan also are deeply flawed. Three of them tangled themselves with several men and then a drastic event happened. Rachel must unravel her emotional and memory messes. But Megan, Anna, and those men were not helping.
All these happened along the commute route that Rachel took daily.
While brilliantly developed, the villain was necessarily only shallowly developed. What? He was the monster? And we hardly knew him, other than those things that he lied but we, obviously, did not know those were lies. The real antagonist is Rachel herself and the real genre is redemption. This makes the book less than Gone Girl that has a sharp conflict and a battle.
It is still a highly enjoyable book. If there is any doubt, I recommend it with 4-star in GoodReads.com