Robert Cormier was born on January 17, 1925, in a French-Canadian neighborhood of Leominster, Massachusetts, the town he fictionalized as Monument in many of his books. An outsider who read and wrote to escape, he attended Catholic school, where a nun encouraged him to become a writer. At nearby Fitchburg State College, a teacher submitted one of Cormier's stories to a magazine, and it became his published debut. Soon after college he became a reporter for local newspapers, and garnered several prestigious awards. He worked as a journalist for 30 years, publishing short stories in national magazines, until his profits from novels allowed him to focus full-time on novels. He became a highly renowned and award winning journalist. As soon as he was financially able he made the shift to writing full time. He then began to sell short stories to magazines, and then advanced to publishing novels.

Influenced in large part by other coming of age books such as Tom Sawyer, How Green Was My Valley, and Look Homeward Angel, Cormier began to write about the complexities of growing up. The fact that he lived in the same city for all of his life gave him a window into his own adolescence, and make his time as a boy growing up much easier to remember and access. Cormier describes himself as an insomniac, and when his children would come home from dates he would be up writing. He had insights into their coming of age as well, and used that as fodder for his books.

Robert Cormier published his first novel in 1960—an adult novel. His first couple novels were for adults, and while they garnered positive reviews he did not become famous until the publication of his first young adult book in 1974, The Chocolate War. Since its publication, the book has been near the top of the most frequently censored books. The novel incited much protest from parents and teachers, who disapproved of the mature language and themes of a book that was supposed to be for teenagers. The book was considered inappropriate because of swearing, masturbation, violence and a depressing, dismal ending. Cormier spent much of his life after 1974 defending the book, and writing others along similar themes. According to Banned in the U.S.A. by Herbert N. Foerstel, a book that documented the most frequently censored books according to public schools and libraries in the US between 1990–1992, The Chocolate War is number five, just under Huckleberry Finn.

Despite the negative attention garnered by the book, The Chocolate War also won high praise, named as one of the best books of the year by the New York Times, winning a Lewis Carroll award and being named to the "Best of the Best 1966–1978" list by the School Library Journal.

The Chocolate War was inspired by Cormier's son, who similarly refused to sell chocolates at a school chocolate sale, although without the negative repercussions of protagonist Jerry Renault. Cormier considers this particular book to be life changing, as he first broke into the young adult scene and the young adult readers first embraced him as someone who spoke to them.

Cormier's books extend beyond normal young adult books, confronting difficult subjects such as rebelling against conformity, dealing with and overcoming guilt, exploring violent and sometimes psychopathic teenagers and also dealing with ethical implications of some of the choices teenagers are forced to make.