Onion John is set in the late 1950s in the tranquil rural town of Serenity, located near the Munkachunk Mountains and Musconetty Creek. This fictional setting is modeled after Belvidere, New Jersey, a county seat close to Krumgold's home with a population of around 2,600. Originally settled by German Moravians, this area lies near the edge of the Pocono Mountains.

Serenity is a quintessential small town, featuring one hardware store and a drugstore where boys gather for ice cream. It also has an amateur newspaper, a passionate Little League baseball team, and an engaged Rotary Club. The surrounding terrain is hilly and rocky, yet it supports thriving orchards and gardens.

Onion John resides on the outskirts of town in a run-down house constructed from piled stones. This house includes four bathtubs but lacks electricity and running water. The Serenity garbage dump, situated next to the baseball field, is where Onion John sources his food and supplies.

The fact that Onion John unfolds in the 1950s is crucial, as the scientific progress and aspirations of the time significantly impact the characters. New inventions like electric stoves and automatic door-openers have transformed many small aspects of daily life. The prospect of sending a man to the moon reshapes the characters' understanding of the universe and their vision of the future. Some, like Andy's father, embrace these changes, while others, such as Onion John, find this new world view incompatible with their sense of happiness and security. While technology brings distant moons and planets closer, its focus on facts and automation depersonalizes many life aspects, creating new distances between people.

Onion John is a lively and humorous tale filled with vibrant and animated characters. Told from the perspective of twelve-year-old Andy, the novel employs authentic, youthful language. Its easygoing humor and vivid descriptions draw readers into the story's events and emotions. The narrative also includes intriguing trivia, like the history of Halloween, which adds to its cheerful atmosphere. The story's well-structured plot ties the novel together, with questions posed early on being revisited and answered by the end.

Krumgold uses irony, especially regarding Andy's father and Onion John, to highlight their differing perspectives. Mr. Rusch believes the most valuable gift he can give his son is the chance to "go to the moon," while Onion John sees this as a profound insult: "I've never heard of any father who would send his only son to the moon!" It is ironic that Mr. Rusch, who has been quite opinionated throughout the book, ultimately advises others to "keep an open mind." While Onion John wants to leave Serenity due to the perceived evil in the community, Andy's father insists he should remain so that people will "keep on being goodhearted." Another instance of irony is that Onion John's new home is destroyed when he tries to use the electric stove, an appliance he never wanted. Krumgold notes that the fire might have been the "best thing" to happen to Onion John.

Some readers might perceive that Krumgold depicts women unfavorably in Onion John. The novel primarily features male protagonists. Andy's mother is portrayed as a kind yet frail homemaker who is afraid of ghosts; her main role is to clarify her husband's actions and emotions to Andy. Andy seems to think that women lack insight and intelligence. For instance, he concludes that explaining Onion John's idea for a rain procession to Eechee's mother would be too challenging for her to grasp. The details surrounding the rain procession also present a stereotypical view of women. The ancient tradition involved sacrificing a beautiful virgin by throwing her into...