Fiction by Liane Moriarty.
What would you do if you found a letter with "For my wife, to be opened after my death," written on it in your husband's writing? (He's still alive in this scenario, by the way.)
Well, I don't know about you, but I'd open it. Like a SHOT.
That's what the main character finds at the beginning of this book, but it takes her a little longer to work her conscience around to opening it. And I was surprised at the contents of the letter inside.
Great premise, great story, great cover. I recommend it highly.