[5] During his Chancellor's Speaker Series talk at University of Massachusetts Lowell on December 7, 2012, King indicated that he was writing a crime novel about a retired policeman being taunted by a murderer.

With a working title Mr. Mercedes and inspired by a true event about a woman driving her car into a McDonald's restaurant, it was originally meant to be a short story just a few pages long.

[6] Describing the novel for an interview with USA Today, published on September 18, 2013, King said that while it was started prior to the Boston Marathon bombings, Mr. Mercedes involves a terrorist plot which is "too creepily close for comfort".

Bill Hodges, a recently retired detective from the local police department, receives a letter from an individual claiming to be the culprit, referring to himself as "Mr. Mercedes".

Hodges finds out, with the help of computer-savvy Jerome, how Mr. Mercedes stole the car and drove Olivia (whom he made contact with through his job at the electronics shop) to suicide by leaving eerie sound files on her computer that were set to go off at unpredictable intervals, which escalated her feelings of guilt.

Holly locates Brady and delivers two harsh blows to his head using Hodges's "Happy Slapper" – a sock filled with ball bearings.

Mr. Mercedes received positive reviews, with many critics responding well to the book being different from King's "standard horror stories" and being a "compelling crime novel."

[10] Michael Marshall Smith of The Guardian noted the novel "is firmly positioned in suspense-thriller territory and the non-supernatural world – somewhere King evidently feels increasingly at home.

"[11] Brian Truitt of USA Today gave the novel 3 and 1/2 stars: "With an accidental gumshoe and a freaky serial killer, … Mr. Mercedes takes the old detective genre in an excellent, modern direction".

[12] Sheryll Connelly of The New York Daily News stated the novel is "telling a story that could almost be characterized as sweet except of course for the sociopath on a bloody rampage.

Club was more reserved, writing that the novel opens with its best moment and "sags significantly in the middle, but it barrels toward a memorable conclusion … his tense, propulsive, ultra-fast-paced climax here seems like it was written with the movie in mind".

Her main complaint was "a collection of laughably creaky old tropes at the center … a halfhearted stop at Señor Lazy’s Bargain Cliché Bin … predictable King-isms … a cutout character following a well-worn path".