Mazes and Monsters

From wikipedia:

Mazes and Monsters is a 1981 novel by Rona Jaffe. The novel is a cautionary tale regarding the then-new hobby of fantasy role-playing games. The book was adapted into a made-for-television movie by the same name in 1982 starring Tom Hanks.
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The novel is based in large part on the apocryphal "steam tunnel incidents" of the late 1970s. These urban myths developed during the infancy of role playing games, generally purporting that university students playing a live action version of Dungeons & Dragons or similar game disappeared into the utility tunnels of the school and became lost, and in some cases died of hypothermia or other causes.