This book was reviewed for The New York Times where it was called "the best novel of the year". The book has been used as part of teaching curricula for children at the novel's reading level. It was illustrated at least by Robin Jacques (UK), Brock Cole (US), and Piers Sanford (later).
Reviewing its first sequel in 1986, Kirkus observed, "The first book had a fine balance between childish desire to play with the tiny figures and awareness that, though small, they were real people who ought not to be so manipulated."
Omri gets a cupboard from his older brother for his ninth birthday. With it, he uses a key inherited from his great-grandmother. Omri, unaware that the key is magical and can bring inanimate objects to life, puts a toy Indian in the cupboard. When he awakes the following morning, he discovers that the toy has been brought to life, and has a name: Little Bear (in some editions he is called Little Bull). Soon, Omri's best friend, Patrick, finds out about the magic cupboard and brings a toy cowboy called Boone to his house to test the cupboard's properties. Despite Omri's warning not to put Boone in the cupboard (as Boone and Little Bear will inevitably fight), Patrick ignores his request. Boone and Little Bear start to fight, and Patrick refuses to reverse the process until it is too late and Boone has been shot by Little Bear with an arrow. Omri has a toy World War I medic that could be used to treat the injured Boone, but the magic key necessary to bring the medic to life has gone missing. After a brief adventure with an escaped pet rat, the key is found and Boone is treated.
Little Bear is a demanding character, and ultimately Omri must provide him with a bride, Bright Stars (in some editions she is called Twin Stars). Omri thinks it is best to send Little Bear, Bright Stars and (with Patrick's agreement) Boone back to their own time. Omri gives his mother the key so he is not tempted to bring them back again.