Nap never believed the official report of their death, and has questioned everything about that fateful night. The more he investigates her sudden reappearance, along with her involvement in a police officer's murder, will lead Nap down a rabbit hole that will cause him to lose trust in everyone he loves.
Coben tells the story from Nap's point of view, so following the mental steps he takes to find the truth adds an extra layer to both the readability and the puzzlement of the story. When the reveal happens, the other characters have always assumed that Nap knew the truth but was in denial. Readers know that is not the case.
The likeability of Nap is paramount to this story, and even though he sometimes steps a bit outside the law for his own brand of justice, he is both endearing and sometimes quite witty. Coben is the master of these types of characters while exposing the hidden layers of suburbia.
There are a few elements that don't make sense in the grand scheme of things, but it doesn't matter. This is all about Nap and his quest.