Books that go through multiple publishing rounds usually get the cover reworked for various reasons. Sometimes the cover is redone to "modernize" it, and sometimes it's redone to appeal to a different group of readers. I found six covers for The Homework Machine. Comment on which one you think is the most successful and which is the least successful. You'll have to briefly describe the cover you're talking about so we can follow you. Think about what makes that cover unique as opposed to saying, "the third cover over on the top row..." Use your knowledge of the story to support your choices if needed.