Can anything be as incomprehensibly terrible as the serial killing of children? Yes: a state, a political system, that encourages it by denying the fact of its occurrence.

This blindness to reality, the inability of a government to accommodate the very notion of human individuality of any kind, whether normal or aberrant, is at the heart of the best thriller of the year, Tom Rob Smith’s “Child 44” (Grand Central, 448 pages, $24.99). “The killer,” it is observed, “would continue to kill, concealed not by any masterful brilliance but by his country’s refusal to even admit that such a man existed, wrapping him in perfect immunity.”

Set in the Soviet Union, beginning in 1933 and ending in the early days of Nikita Khrushchev’s rule, this superb novel does not fit into any subgenre of the mystery. It is a police investigation, though not by a policeman. It is a spy story only in the sense that in the paranoia of the Soviet government everyone was regarded as a potential spy, or at least a traitor to the revolution. It is a thriller because — trust me on this — you will find your pulse racing in scene after scene.

It is also a political novel because no book I have ever read, fiction or nonfiction, ever illustrated with such unequivocal clarity what it was like to live in the hopeless, fear-filled Stalinist era of repression, where the best hope for an ordinary citizen was to be invisible, to be as gray, subservient, uncomplaining as possible. In the face of an intolerable, intolerant system of inhumanity, the best hope for survival was to accept hopelessness.

“Child 44” opens in Ukraine, a state in which the population was systematically, purposely, starved to death. As an entire village slowly dies, a near-miracle presents itself to a young boy, Pavel, and his even younger brother. They see a cat. Scrawny, yes, but a veritable feast on frightened feet compared with the bark the townspeople had been chewing in desperation for some nutrition, or the clods of earth picked through for a few ants or insect eggs.

The hunt for the cat becomes a matter of life and death, and Mr. Smith, in just a few pages, conveys the boys’ gut-wrenching terror of failure. Then, just as success seems assured, the situation becomes more dire. While Pavel hunted the cat for food, someone else had hunted him for the same end.

Skipping ahead 20 years, Leo Demidov, a member of MGB, the State Security force, is a loyal citizen who believes in the Soviet Union, committing heartless atrocities against its people in order to maintain the state’s perfect order.

He is sent to Rostov-on-Don to investigate the death of a young boy found naked with his mouth stuffed full of dirt and his abdomen savaged. The boy’s family wants a murder investigation but the state maintains that there is no crime in the Soviet Union, so Leo visits them, intimidating them into accepting the boy’s death as an accident. To dispute this would be contrary to the state’s position, hence an act of treason — enough to send them all to a gulag.

Back in Moscow, Vasili Nikitin, second in command to Leo’s division of the MGB, despises his superior for being smarter, better looking, and more successful, and will do anything to ruin him. He denounces Leo’s beautiful wife Raisa as a spy. Although not proven, the very accusation is enough for them to be executed, or sent to a gulag, which is pretty much the same thing, only slower. In order to humiliate Leo, Vasili, who has all the charm of a funnel spider, allows him to live, sending him to a small town as merely a member of the state militia. “In a classless society,” Mr. Smith writes, “the militia were near the bottom of the heap.”

It is here that Leo learns a serial killer is on the loose. Realizing that he is the only one who can stop him, he vows to catch him, even knowing that it could cause the death of himself and his wife, as well as his parents and anyone who helps in the investigation.

It is impossible in only one column to do justice to this masterful first novel, as there are so many scenes of excruciating suspense, unexpected decisions by fully realized characters, and a complex plot in which, ultimately, every piece fits perfectly. It is, to use the most overused word of the decade, awesome.

Mr. Penzler is the proprietor of the Mysterious Bookshop in Manhattan and the series editor of the annual Best American Mystery Stories. He can be reached at ottopenzler@mysteriousbookshop.com.