Stephen King’s 1986 novel It is widely considered to be one of the most frightening stories ever written. The book’s cast of characters clash against a monster that can assume the form of their worst fears, in a town called Derry that is itself a source of evil. It examines themes of friendship, family, grief, fear, and memory.

The novel jumps frequently between past and present, but the structure of the story told in It can be divided into two parts: childhood and adulthood. In the first half of the novel, seven children in Derry become increasingly aware of a monster that is killing children. The group comprises Bill Denbrough, Richie Tozier, Beverly Marsh, Ben Hanscom, Mike Hanlon, Eddie Kaspbrak, and Stanley Uris.

Bill, the leader of this group of seven kids that will come to be known as the Losers’ Club, suffers the greatest loss among his friends: the first death shown in the novel is his brother, George. The monster It appears in a storm drain after a flood and kills George after his newspaper boat goes into the drain.

Each of the character’s childhood encounters with It are presented in great detail, leading to the moment in which they met—and joined—the Losers’ Club. They eventually fight It and believe they have killed the town's sinister tormentor. They make a promise that if It ever returns, they will come back to finish what they started. Six of them leave Derry. Mike Hanlon stays behind and becomes the town librarian, keeping a watchful eye on the town.

It always awakens in twenty-seven-year cycles. When the murders begin again twenty-seven years later, Mike calls each member of the club and reminds them of their promise, asking them to come back and stop It. Five of them return, but Stanley Uris commits suicide, rather than face the monster again.

After reconvening in Derry, the second half of the story follows the remaining six adults as It reappears in their lives. They are each astonished to realize that they have forgotten everything that happened to them as children, but Mike is the exception. Because he never left Derry, he never forgot.

The remaining members of the Losers’ Club eventually return to the sewers for the final confrontation, where It takes the form of a huge spider. They manage to weaken It through the bond of their friendship, and Bill is able to pull out the spider's heart and destroy it. During the fight, they also see that It is pregnant, and they destroy its eggs before leaving the sewers. During the fight, Derry begins to flood, and by the time they are topside—minus Eddie, who is killed by the spider—Derry is collapsing.

They each leave Derry, except Mike. They try to stay in touch but realize that they began forgetting everything again—even each other—as soon as they left the town. As the novel ends, they know that they have succeeded and that It is dead.

In addition to the narrative, It is interspersed with several “Derry Interludes” written by Mike Hanlon in his role as amateur Derry historian. Each Interlude focuses on a different disaster, or act of violence, in four of the different cycles in Derry’s past, showing that It has been plaguing Derry for far longer than the children ever suspected.

It is a masterful examination of fear, the divide between children and adults, belief in monsters, and much more. King's twenty-second book, It won the British Fantasy Award in 1987 for Best Novel.