The first question: Is Jay Gatsby a mystery? On one hand, he's out in the open-- everyone goes to his house, everyone recognizes his car. On the other, what does anyone really know about him?
The second question: Is The Great Gatsby a mystery? On one hand, it's not a police procedural or the story of solving a crime. One the other, aren't we following Nick as he's handed clues about why people are doing what they're doing? Does that make this a "whydoneit" instead of a "whodunit"? [Hey. Not so fast. Click that link.]
Please comment to this post with your thoughts on both questions.