The Great Brain Reforms, by John D. Fitzgerald, was published in 1973 by Dial.
The year is 1898, and the best con man in Adenville, Utah, is the infamous twelve-year-old Tom Fitzgerald, “The Great Brain.” A year at the Catholic Academy for Boys certainly hasn’t dulled Tom’s love for money—he’s no sooner off the train than he begins scamming his own brother! By the end of his summer break, Tom has tricked all his friends out of everything they own. He even outwits three professional crooks who come to swindle the whole town. Tom thinks he should be the most popular kid around: He has all the good toys, and he’s saved his townspeople. Tom really begins to rake in the dough when he sets up business as a raftsman. But when he endears the lives of two friends, his brother J.D. decides it’s time for the Great Brain to reform. And that’s how the case of The Kids of Adenvillev s. The Great Brain is tried in the Fitzgeralds’ barn one summer day.