Why are Sarah Silverman and other authors suing ChatGPT?

Comedian Sarah Silverman sued ChatGPT-maker OpenAI for copyright infringement this week, joining a growing number of writers who say they unwittingly built the foundation for Silicon Valley's red-hot AI boom. Photo: AP

Ask ChatGPT about comedian Sarah Silverman's memoir The Bedwetter and the artificial intelligence chatbot can come up with a detailed synopsis of every part of the book.

Does that mean it effectively "read” and memorised a pirated copy? Or it scraped so many customer reviews and online chatter about the bestseller or the musical it inspired that it passes for an expert?