What Makes A Book A Children's Book?

• A central character (protaganist) who is the age of the intended audience.
• Central issues of the story concern children in some ways.
• A straight forward story line.
• A linear and limited time sequence in a confined setting.
• Language is concrete and vivid and not overly complex.

Not too sure if the last 3 points really apply anymore. Children's book is getting more and more sophisticated. Even the age of the protagonist may not be a good gauge now.

However, the 5 points above do serve as a guide. : )