The story begins with Greg introducing his family, including his parents, his older brother Rodrick, and his younger brother Manny. Greg soon finds himself facing a series of unfortunate events caused by Rodrick's pranks, including being locked in the basement, having his diary read aloud to the entire school, and being forced to join the wrestling team.
As Greg tries to cope with Rodrick's antics, he also contends with other middle school problems such as dealing with bullies, trying to impress girls, and navigating the social hierarchy of his school. Amidst all the chaos, Greg tries to maintain his sense of self and keep his sanity intact.
Eventually, Greg finds an unlikely ally in Rowley, his best friend, who helps him through his troubles and provides moral support. As Greg learns to stand up for himself and stand his ground against Rodrick, he gradually discovers that his brother is not as bad as he thought and that they may even have a chance to form a stronger bond.
"Diary of a Wimpy Kid: Rodrick Rules" humorously portrays the trials of growing up and the dynamics of family relationships, capturing the essence of middle school life and the challenges of navigating adolescence.