John Martin's Book was a children's magazine aimed at five- to eight-year-olds. Martin Gardner wrote that it was a "pioneering publication" and the "most entertaining magazine" aimed at this age group published in the US. Priced from 10 to 50 cents over its twenty-year run, it was primarily purchased by middle and upper income families due to its cost. After the end of John Martin's Book, Shepard became juvenile director for the National Broadcasting Company.