Here's a breakdown of the main idea:
* Greg's Problems: Greg is a typical middle schooler who struggles with schoolwork, social situations, and his family. He is constantly in trouble, often due to his own bad decisions.
* The Threat of Military School: Greg's parents decide that he needs a stricter environment and consider sending him to a military school.
* Greg's "Good Boy" Strategy: Greg, terrified of military school, tries to change his ways and become a "good boy" to convince his parents that he can handle regular school.
* The Chaos Ensues: Greg's attempts to become a model student are hilariously misguided and lead to even more trouble for himself. This includes accidentally setting off the fire alarm, ruining his sister's play, and more.
* Greg Learns a Lesson: Despite all the chaos, Greg starts to realize that being true to himself is more important than trying to be someone he's not. He also learns that even when things are tough, his family loves and supports him.
The book explores themes of family, identity, and learning from your mistakes. It's ultimately a story about finding your own way even when you feel pressured to conform.