For example, there are a lot of reading challenges that include prompts like "Read a middle-grade horror book", but, especially for bigger more popular challenges, the books added can be filled with books aren't middle grade, aren't horror, or both.

It would be really nice if the person making the challenge could use the same setup as filtering your to-read list to filter which books can be added to a prompt. So you could say, only books marked BOTH horror and middle grade can be added.

I know this would be a ton of work, but it would be really cool to see and really improve the quality of the books when you look through challenge prompts for recommendations.