Gone Girl, by Gillian Flynn
One-line review: Girl gone, be gone, bygones be bygones?
Review (minor spoilers): Amy goes missing on her fifth marriage anniversary, and as the police start investigating, suspicion begins to zero in on her husband, Nick. There are signs of a struggle in their house, overturned furniture that looks like it was overturned after the fact, broken glass, and later the police even find evidence of a sloppily cleaned-up blood stain in the house. Nick lies to the police, one lie after another, to cover up for the fact that his marriage with Amy had been on the rocks for some time. Things get worse when Nick's sister, Go (Margo), finds that he has also been having an affair with one of his students for over a year. Amy had, it seems, made one last attempt to resuscitate their marriage by leaving several clues in the form of letters, like she used to do, on the eve of their marriage anniversary. Nick figures these clues out, one after the other, but they bring him or the police no closer to cracking the case. Circumstantial evidence mounts and the rising evidence of a motive all point to Nick. Then there is the huge life insurance policy that would accrue to Nick in the event of Amy's death.