The three plaintiffs allege that when prompted, ChatGPT will produce a summary of their works. They claim this is copyright infringement, as they did not consent to their books being fed to ChatGPT.

How can they have a case? How many sites, interviews, social media posts have content that goes over summaries of their books?

Silverman herself has probably gone over the book context in enough posts and press releases/interviews to give ChatGPT all the context it needs.