What book did Suzanne collens have the most fun writing?

Suzanne Collins has never explicitly stated which of her books she had the most fun writing. However, she has mentioned that she enjoyed the process of writing "The Hunger Games" trilogy, specifically because she found it challenging and rewarding to explore the themes of survival, rebellion, and the power of hope.

She has also expressed fondness for her middle-grade book "Gregor the Overlander", highlighting the fun she had creating the world and characters within it.

Ultimately, it's likely that Collins enjoyed the creative process of writing each of her books in its own way, but she has not publicly favored one over the other in terms of enjoyment.