What I think this book is about is that this world were Jonas lives everything is destroyed and its a community that doesn't know about the world. After I "interviewed" the book I thought that The Giver is a man who remembers everything of the past. I would describe it as a world or community of lost people.
What Lowry is trying to say is that this book is for the children of the future that they shouldn't let the government control the world/ community and also so they don't make the same mistakes that Jason or The Giver makes during the book. (What I think).
This book is going to be about a community that has a lot of problems and The Giver is a very important man in the community that helps the community to be a better place. And Jonas is a man who has a lot of knowledge.