Here's why:
* First-person narration: The story is told from Greg Heffley's perspective, using "I" and "me." This creates a personal and informal tone.
* Simple language: The writing style is straightforward and uses everyday language, often slang and colloquialisms.
* Humorous tone: The book is filled with humor, often through exaggeration and absurdity, which contributes to its informal nature.
* Focus on everyday life: The story centers on Greg's experiences in middle school, dealing with friends, family, and school life, creating a relatable and informal setting.
While the book has a narrative structure, the informal language and personal perspective make it feel like a diary entry, rather than a formal literary work.