Stephen King's Mr. Mercedes has a pretty good hook which quickly draws us into the story: a retired police detective, bored and quite possibly suicidal, gets a new lease on life when he starts getting taunted by "the one that got away", a homicidal maniac who ran down a whole bunch of people in line for a job fair. Detective Bill Hodges now has a reason to live again, as he decides to chase down "the Mercedes Killer" himself, rather than turn things over to his former cop colleagues.
This maybe isn't first-tier King, as the plotting and characters are fairly simple. Bill Hodges, for example, is totally good and totally likable (if sometimes flawed in his thinking), while the Mercedes Killer is totally creepy and totally evil. This doesn't make things horrible, just a little less interesting than many of King's other books. There's good suspense throughout, though, and a few story highlights. These include a gory poisoning death that makes the book feel like the classic King of old, and a long set piece near the end, set at a boy-band concert attended by 4000 screaming pre-teens, where our heroes attempt to prevent a tragedy that would make the Mercedes Killer's first act of terror seem like a hangnail.
There's some good humor throughout, too. The way King describes the insipid daytime TV that retiree Hodges is watching day in and day out at the story's start makes us completely understand why the barrel end of Hodge's service revolver is starting to look disturbingly good to him. Talk about horrific!
If this novel was one of those 800-page affairs of King's, I'd be harder on it. But, as it's fairly compact, I'm basically okay with its more simple, modest pleasures. You get a decent cat-and-mouse detective plot, a little romance, some likable supporting characters, and at least three or four instances where you'll be turning the pages very quickly. Hey, not everything has to be Duma Key or 11/22/63. Sometimes "pretty good" is perfectly fine.