In the novel Trouble, Gary D. Schmidt's writing style feels very casual and conversational, just like the thoughts of a teenage boy. Schmidt especially creates the conversational style through interjections and repetition. The effect is that, even though the narrator is a third-person narrator with a limited focus on Henry, the words of the narrator sound like Henry's thoughts.
An interjection is a word or phrase added to a sentence to express emotion. Multiple examples of interjections can be seen throughout the book. One example occurs in the first chapter when the narrator describes the uniform Henry must wear to the John Greenleaf Whittier Academy for seventh and eighth graders:
... where all seventh- and eighth-grade students wore uniforms involving a white shirt, blue blazer, red-and-white tie (the school colors), khaki pants, black socks, black loafers, and--no kidding--red-and-white boxers. (p. 3)
The interrupting phrase "no kidding," surrounded by dashes, counts as an interjection that helps express the narrator's sense of absurdity. The narrator sees how ridiculous it is for a school to require a student to wear specific boxers and is expressing his sentiment in an interjection, just as a teenage boy would, using the same words a teenage boy would use.
Repetition also helps create a casual, conversational style that mimics a teenage boy's voice. Repetition can be found throughout the novel, especially as Henry reflects on his father's philosophy about staying away from trouble. Another example of repetition can be seen in passages describing Franklin:
... since [Henry] could never hope to match the records that Franklin Smith--Franklin Smith, O Franklin Smith, the great lord of us all, Franklin Smith--had put up on the wooden Athletic Records panel for his rugby play. (p. 3)
Repetition of the name Franklin Smith plus the phrase "great lord of us all," words a teenager would say, creates the narrator's verbal irony, irony that helps capture Henry's true feelings: Henry doesn't see why Franklin should be seen as such a wonderful person.