It depends with which concepts someone is already familiar. To me the only really new concept was the lifetime and ownership one, all others have just a different syntax plus here and there some extra goodies. As example, when I saw the match keyword I thought "cool, Rust has a keyword for guards".
I learned Rust shortly after 1.0 was released. The real obstacle for me to overcome was to build a mental concept of what Rust is. Something that wasn't really communicated while reading the first pre-release Rust book.
You have to read a lot to get an idea of Rust, it should be the other way around – a common mistake done by almost everyone teaching something. Ideally the first chapter would be a buzzword free, Rust code free chapter about how Rust works superficially and why there is a need for yet another computer language. It should describe what kind of tools and concepts in Rust exist and which problems they solve. This is better than introducing somewhat complicated concepts/tools and trying to explain how they fit into the big picture at the same time.
Ideally there would be an introduction like this:
A program needs a structure, variables, control flow, tools... blablabla... this leads to some common problems [some easy examples] and [this] are some concepts Rust invented/uses to solve them.
In later chapters the abstract ideas would be "converted into Rust". Also don't go too much into detail. I don't think for example that a representation of the memory layout of a vector helps much. At first I just need to know there is a thing where I can put objects of the same type into, how it is implemented is not that important for a beginner. It's better IMHO to know how to do something right, than why something is right. This reduces the mental burden in the beginning of the learning phase. The why is something that you learn over time – or maybe you are not that interested and skip it forever, also a valid thing to do.
Overall the Rust community does a stellar job providing so much help in so many different ways – /r/rust on Reddit is really awesome – thanks for the book and your open mind to ask for feedback.