In my dream world, you take that book plus information about yourself (how good of a programmer you already are), feed that into AI and get a customized version that is much better for you. Possibly shorter. Skips boring stuff you know. And slows down for stuff you have never been exposed to. Everyone wins.

Yes, and you get to ask questions. So, interactive.

Why do I need a machine to do that?

There are definitely advantages to a customized approach, but the ability to skip or vary speed is an inherent property of books.