After having read it, I can say this is probably the best book to explain how ChatGPT (and LLMs) work (written by Stephen Wolfram, who excels at explaining complex topics simply, so perhaps not a surprise)
There's also a blog post form for those wanting to read online.
Really like how accessible but also thoughtful this book is.
Instead of jumping into the mechanics of ChatGPT (that it gets to) the first part of the book is about the evolution of neural nets (and deep learning), limitations and the concept of computational irreducibility.