Stephen King may be the acknowledged grand master of horror fiction, but he has always known that the everyday demons hiding behind the screen doors of small-town streets can chime with our deepest terrors just as effectively as the evil creature in the sewer. Mental illness, addiction, poverty, childhood trauma, alienation – these are the real monsters that crouch beneath the surface of our lives, and they stalk the pages of most of his fiction in one form or another, even in stories that appear to be concerned with more obviously supernatural forces of evil.

There is nothing paranormal about Mr Mercedes, his 57th novel. It's a good old-fashioned, race-against-time thriller with all the favourite tropes of the genre lined up from the off: the maverick detective who must operate outside the confines of the law; the killer with a personal vendetta and an unhealthy relationship with his mother; the band of misfits who cooperate to stop him before he can carry out his murderous plan. You might even say that these building blocks of the genre are familiar to the point of cliche; more interesting is the part that social realism plays in the machinery of this story. Mr Mercedes opens in 2009, as the recession tightens its grip on an unnamed midwestern city. A job fair is to be held at the sports stadium; the desperate unemployed turn up to queue in their thousands overnight. As dawn breaks, a sleek 12-cylinder Mercedes SL500 emerges out of the fog at speed and ploughs through the densely packed line, killing eight people and injuring 15 more. It's a sledgehammer of a metaphor: a luxury car heedlessly crushing those who are already victims of inequality. Immediately King has snared the reader's interest; is this killer politically motivated, and whose side is he on?

Since this is not a whodunnit, we learn almost immediately. The Mercedes killer is 28-year-old Brady Hartfield, still at large a year after his deadly joyride. Across town, detective Bill Hodges, who was working on the case before he retired, is contemplating suicide when he receives a letter purporting to be from the Mercedes killer. From this point the novel becomes a battle of wits between Hodges and Brady as each tries to lure the other into his trap.

The economic decline of America's industrial cities infects the atmosphere of the novel but is never really brought to the fore in the way the initial symbolism implied. Brady is moved by nothing so significant as a cause – he is merely an unremarkable man with a fragile balance of mind, driven by a series of mundane accidents and bleak circumstances to hate the world and force it to take notice of him. He represents a plausible evil; it's impossible not to hear echoes in his story of other troubled young American men who have opened fire in crowded schools or cinemas, as King peels back the layers to understand how a killer like Brady is formed: "The truth is darkness, and the only thing that matters is making a statement before one enters it. Cutting the skin of the world and leaving a scar. That's all history is, after all: scar tissue."

This psychological examination comes somewhat at the expense of tension and narrative pace, which only picks up towards the end. Mr Mercedes is rooted firmly in the small-town realism for which King is frequently celebrated and which is often overlooked in the thriller genre; the stakes are fairly low here and Hodges is an unprepossessing hero, just as Brady is a banal kind of monster. Perhaps the most chilling aspect is how many potential Brady Hartfields there might be lurking across recession-blighted America, blaming society for what they become; this is the real fear that King sows in his readers' minds. You'll never feel quite at ease in a public gathering again.