I actually read this all the way to the end because I wanted to see how the plot turned out, but despite the Stephen King blurb ("a master") and the NYT recommendation, this book's illogic appalled me.
So, modified spoiler alert: I won't give away the ending, but need to discuss some key plot points.
Mark Novak is a private investigator working for a Florida firm that helps to free death row convicts. His wife has just been killed, and he has sort of gone off the reservation. Partly to save his hide, his boss sends him to southern Indiana on a case the firm normally would never take. Years before a teenage girl died in an underground cavern, and her body was brought out by a caver named Ridley Barnes. Now Ridley wants the firm to investigate whether he in fact killed the girl, because he can't remember.
After Mark arrives, he is greeted with suspicion by seemingly the whole town, because no one likes Ridley, and Ridley himself is clearly unbalanced, they believe, talking as though the vast cave, known as Trapdoor, is a living creature that instructs him what to do when he is in there.
Now, huge breakdown No. 1. Mark is approached at his hotel by a woman who says she is the dead girl's mother, and they talk over dinner. A local reporter then calls him up, having heard he is trying to reopen the case, and Mark tells him about talking to the mother. It turns out the mother has been dead for years -- not only does the reporter NEVER TELL HIM THAT, but writes a news story saying that Novak has lied about talking to a dead woman. And the local sheriff, who was in love with the mother years before, believes Mark has made up the story, even though there is NO PLAUSIBLE REASON for him to do that.
Not long after, Mark is abducted on a local roadway by masked men, is blindfolded, put into the Trapdoor cave, and barely survives until Ridley himself finds and rescues him. And then, again FOR NO PLAUSIBLE REASON, the sheriff and everyone else believe Mark crawled into the cave himself in his underwear and do not investigate the reports of him being abducted.
Reading back over this, I am amazed I bothered to go through the remaining 250 pages or so after encountering such fundamentally unbelievable plot drek, but I did.
And so, not "a master," Mr. King. Not at all.