What is i know what you did last summer book?

"I Know What You Did Last Summer" is a horror novel written by Lois Duncan and was first published in 1973. The story follows four teenagers, Julie, Helen, Ray, and Barry, who are involved in a hit-and-run accident that results in the death of a young boy on a country road one night.

The teenagers make a pact to keep what they did a secret, but a year later, they all begin receiving mysterious and threatening notes that seem to know what they did last summer. As the mystery unravels, the teenagers must confront their guilt, paranoia, and fear as they are hunted by a mysterious figure seeking revenge.

The novel was adapted into a successful film of the same name in 1997, starring Jennifer Love Hewitt, Sarah Michelle Gellar, Ryan Phillippe, and Freddie Prinze Jr. The film spawned two sequels and remains a cult classic in the horror genre. Lois Duncan's novel is known for its suspenseful storytelling and well-developed characters, making it a popular choice for fans of thriller and horror fiction.