His father was in the United States Navy, so his family moved many times during his childhood before settling in Honolulu, Hawaii.
While attending school at the Honolulu Museum of Art, Mayer decided to enter the field of children's book illustration.
Though his professors feared the young artist would never be good enough to make a living as an illustrator, Mayer was not dissuaded.
[citation needed] During his spare time from his job at an advertising agency, the artist created a completely new portfolio.
These new sketches persuaded editors at Dial Press and Harper & Row to give him some illustration work.
Critics compared the book unfavorably to Maurice Sendak's Where the Wild Things Are (ironically Sendak himself found no such comparison and enjoyed Nightmare; having been a friend of Mayer's),[4] but children and their parents loved the story and it became very popular, with at least 14 editions being released since its publication in 1968, and was featured on Reading Rainbow.
An animated special was made, which faithfully followed the book and added two small sections where the boy is playing outdoors at sunset and reflects how the monster will soon come, as well as arranging his planes and toy soldiers around the closet to form a "defense force".