What is 1 Major lesson

I think the importance of friendship is an important theme in the book. One of the primary conflicts in the book is the broken friendship between Greg and Rowley. The two are clearly close friends. They begin the summer together hanging out at the country club. Greg is the dominant of the two boys. He gets Rowley to go along with his antics, but it’s not until Rowley takes initiative and walks away from Greg during the lawn care episode that the friendship flounders.