The Reivers is about a stolen car, a stolen racehorse, a brothel, a stowaway, and some mules—all told to us through the eyes of an eleven-year-old boy. So we know we're going to have some fun with this.
The tone remains lighthearted throughout, as Lucius takes us on his childhood adventures and describes the people who fill his life. From the opening scene, when Boon tries to shoot Ludus for calling him names, to Lucius's internal battle between good and evil, everything we get is laced with humor. "If I've got to tell more lies, at least let it be to strangers" (3.61), he says, for example, in a childlike effort to justify his actions.
Yet we won't belittle the seriousness of parts of the novel. Lucius does encounter some pretty heavy stuff, such as sexism, racism, violence, and corruption. Perhaps playfulness is how eleven-year-old Lucius processes the world around him and makes sense of the things he encounters for the first time. Though he's narrating the events to us as an adult, we've gotta remember that he was a child back at the time they happened. His telling us the events as a playful eleven-year-old would is all a part of his process of understanding what actually went down with him.