I discovered Jon Klassen through the student book club I facilitate for. The book:
was on our list. The kids just loved it! I saw that there was another hat-related book and we had to check that out too. It's called:
The endings are great for discussing how authors sometimes don't spell out what happens at the end of a story, but you have to infer what happened. I also, of course, like the latter book for a discussion of the ethics involved. The fish gives many excuses as to why he is keeping the hat, even though it's not his. My kiddos wrote about their feelings on the matter.