** spoiler alert ** 
 Imagine that you fell deeply, truly in love, but lost them to someone else. Years later you try to reconnect, only to find that nobody seems to know who she was. 
 It's a story concept worthy of Hitchcock, maybe with a dash of Kafka. Harlen Coben spins up a pretty effective thriller in the standalone "Six Years," where the hero fights against a terrifying wall of secrets, lies and murder... and the only problems are that the ending isn't really conclusive, and the main character seems selfish in his relentless quest. 
 Six years ago, Jake Fisher fell passionately in love with Natalie Avery. But suddenly she dumped him, married an old boyfriend named Todd and forced him to promise to leave "us" alone. And for six years, he kept the promise. 
 Now Jake learns that Todd has just died, and goes to his funeral in hopes of getting closure with Natalie... only to see his wife of TWENTY years is definitely not her. Baffled and worried, Jake starts searching for his onetime lover, and discovers that not only does the artists' retreat where they met not exist, but no one will admit to knowing anything about Natalie. 
 Well, until the hit men show up and try to kill him, demanding to know where Natalie is. Soon Jake has been suspended from his job and is being followed by the increasingly suspicious police -- which only spurs him further into his quest. But he soon discovers that uncovering the truth could be deadly to more than just himself -- it could destroy Natalie and several other people as well. 
 "Six Years" gripped me like a vise for most its length. Coben's writing is smooth and workmanlike -- not particularly detailed or atmospheric, but with some clever turns of phrase and some fairly exciting action scenes (a hit man's shattering neck sounds like "wet paper-mache"). And he has a rare knack for spinning up a sense of thick, foggy suspense, building up plot twists and murky secrets that are layered over each other. 
 And he weaves that plot together well. The assorted clues quietly fall into place one by one, bringing together mobsters, hit men and the ugly secrets of academia into one big sordid mass. In this, I must tip my hat to Mr. Coben... 
 ... but then in all falls apart in the last few chapters. When a pesky supporting character is brutally gunned down, I started to have the nagging suspicion that Coben had run out of story to tell before he had wrapped the plot threads up. The whole REASON Natalie is on the run is left hanging, unresolved and unsatisfying, at the book's end -- nothing has actually been fixed or dealt with except the "relationship issues." It feels like Coben is keeping his options open for a bad sequel to handle everything he DIDN'T cap off here. 
 Jake starts off as a fairly ordinary protagonist with a thick romantic streak, and at first you feel sorry for him about "the one that got away." But that sympathy starts to trickle away when he refuses to stop looking for Natalie, even though he's repeatedly told that his quest may either get her killed or cause her to kill HERSELF. He just refuses to believe that things could turn out badly for her, or that he has any kind of responsibility towards her. 
 Eventually, it feels less like he loves her truly and more like he wants to PROVE that he was her one bestest truest luv. It seems less like love than obsession, and his constant nattering about the brief time they were involved becomes tiresome. 
 And like Rebecca, Natalie is a nebulously lovely figure that can only be pieced together like a puzzle. When she DOES show up, we don't really get any answers about how she got there, why, or where she's been. Nothing. 
 "Six Years" grinds along nicely for most of its length, but the hard-won mystery is never concluded, and the hero's blind doggedness becomes an irritant. This standalone shows Coben's skill, but he sells himself short where he's strongest.