Of Mice and Men was Steinbeck's first attempt at writing in the form of novel-play termed a "play-novelette" by one critic. Structured in three acts of two chapters each, it is intended to be both a novella and a script for a play. It is only 30,000 words in length. Steinbeck wanted to write a novel that could be played from its lines, or a play that could be read like a novel.
Steinbeck originally titled it Something That Happened (referring to the events of the book as "something that happened" because nobody can be really blamed for the tragedy that unfolds in the story). However, he changed the title after reading Robert Burns's poem To a Mouse. Burns's poem tells of the regret the narrator feels for having destroyed the home of a mouse while plowing his field.
Steinbeck wrote this book and The Grapes of Wrath in what is now Monte Sereno, California. An early draft of Of Mice and Men was eaten by Steinbeck's dog. As he explained in a 1936 letter:
My setter pup [Toby], left alone one night, made confetti of about half of my [manuscript] book. Two months [sic] work to do over again. It sets me back. There was no other draft. I was pretty mad, but the poor little fellow may have been acting critically.
In the introduction to Penguin's 1994 edition of the book, Susan Shillinglaw writes that Steinbeck, after dropping out of Stanford University, spent almost two years roaming California, finding work on ranches for Spreckels Sugar where he harvested wheat and sugar beets. Steinbeck told The New York Times in 1937:
I was a bindlestiff myself for quite a spell. I worked in the same country that the story is laid in. The characters are composites to a certain extent. Lennie was a real person. He's in an insane asylum in California right now. I worked alongside him for many weeks. He didn't kill a girl. He killed a ranch foreman. Got sore because the boss had fired his pal and stuck a pitchfork right through his stomach. I hate to tell you how many times. I saw him do it. We couldn't stop him until it was too late.