I appreciate the example, but here's where I think it differs as an analogy of what LLMs do:

A summary doesn't have infinite or variable depth. If you read the summary of a non-fiction (I'll limit my argument to that, as another poster pointed out) book, and either aren't convinced, or want to learn more about the matter, you'd have to purchase the book.

An LLM that has ben trained on the book, if somehow designed not to hallucinate, would be able to answer any question you have about the book at any depth, seamlessly blending in material from other books to answer a question or explain a concept. That seems like an entirely better experience than reading the book from start-to-finish. I don't see how the original can compete.