This is a long chapter book for much older children. It is about a boy who lives in a "perfect" world. Fountas & Pinnell label it as a Level Y book and I think that is fair and appropriate considering the subtle themes, complex plot, social problems with explicit details, fantasies, and analyzing by the reader. Level Y means this would be a book for 6th graders which I think is perfect. I personally heard this story for the first time when I was in 4th grade while my teacher read it aloud to the class. Most of my classmates did not seem to understand it or even be very interested in it. I understood it and enjoyed it, but it was somewhat confusing even though I was a very advanced reader. I read it over again in 6th grade and appreciated it and understood it much more. I may be comfortable reading it aloud to a 6th grade class if we stopped very often to review and discuss what we've read. I may assign it to an advanced reader to read alone.
As an activity, I would break my students into groups of 4-5 depending on reading levels and comprehension. I would give the assignment of creating their own imaginary society like Jonah's community in the book. What would the rules be? What would each job consist of? Who would live there?