it's a visual novel where you crank to get further clues, notes, chats, and so forth (B button). Plus to go to next level crank (with A button) to also try to get hole in one on the links!
The developer's description and comment answer your question. This is not "just an Agatha Christie novel in playdate game form." This is a visual novel that uses a control interface and gameplay mechanics you'd typically find in a golf game. This is a marriage of both gaming concepts, visual novel and golf game. If you're looking for a golf game, this probably isn't it. If you like Agatha Christie and golf games, this may be up your alley.