I think the author wrote this book because he wanted to teach his readers that bravery is important. For example, Dooley's father tells him that the important thing about giants isn't how big they are it's how brave they are. Also, the way Dooley saves his friends and grows into a full-sized giant is by standing up to a really mean monster called a snortsnoot. So Jack Kent shows that bravery is important because bravery is not only the thing that Dooley wants the most, but it is also what saves him and his friends.
I would definitely recommend this book to anyone. I think the pictures are great and the story has a good lesson. Also, I have a strong personal connection to this book because I read it and loved it when I was a little kid.