Why? ChatGPT is great for learning stuff, but sometimes you just want to go deep and read an entire book about something.
For example, there's a great talk by Stephen Wolfram that just goes over my head (https://www.youtube.com/watch?v=fLMZAHyrpyo), so I copy/pasted the transcript into the GPT and it generated a textbook that goes deep into all the topics from that video (https://instabooks.ai/products/bbacb7a2-deab-df76-e20b-1fea2...).
PS: If you don't have ChatGPT Plus (or can't access the GPT for some reason), feel free to use the old school HTML form on the website to generate a book: https://instabooks.ai