But if it's such a great pet, why is it being sold cheap?
It's really cute. I would think that most children wouldn't get the emotional bits and would just think it was a funny book about having a rhinoceros for a pet. And it is funny. There's definitely no bad message to this. I don't think a child would actually get the impression from this that rhinoceroses make good pets. It's more or less a book of imagination, whimsy, and nonsense, and Shel Silverstein is a master of all three.
Message
None.