What are your standards of learn?

I would say you have to be familiar with a large part of the standard library, de facto standard crates, and most language features, plus have the experience to write code and deal with compiler errors effectively. No way anyone is doing that in a couple of weeks by reading one book. At least for Rust.

Maybe for something a lot simpler like Go it's plausible, but even then I doubt it. You're not going to know about any of the common gotchas for example.