As either a Reading Challenge creator or entrant, I'd like the ability to warn that a single book is currently being used to complete multiple prompts on a Challenge.

I'm in a few challenges where I've added multiple books to each prompt, and some of those books are in multiple prompts.

Maybe the easiest way to do this would be to visually identify which book is currently being used to count a Prompt as "completed"? I could scan those and remove duplicates in other prompts.