K&R is excellent. One of the things that makes it stand out would be almost irrelevant today, it has an excellent hand-made index. If you're wondering about, say, arithmetic conversions, the index gets you straight to the page which lists exactly what you needed. Wondering when to pick enum over #define? Again, the index has your back.

Today online you've got full text search, maybe you find two, three hits that are irrelevant, but it's so cheap you barely care. And in a book today the index is probably auto-generated (hiring somebody to write an index is not a thing these days) and so it's almost useless with dozens of irrelevant entries, but hey, like I said, full text search, so who cares?

Because C is such a small language and it was essentially finished when the book was written, they get to do a pretty complete survey while also teaching you, so you read the book once, now you understand C pretty well. The Rust book is much better than C++ books I tried, but because Rust is still immature there are big sections that are being rewritten or have already been rewritten, and of course the whole book can't be reordered and started over each time, so overall it's uneven.

I am reluctant to buy a printed Rust book because of that immaturity. My (second edition) K&R is still a pretty good survey of the language. Are there things it doesn't cover? Yes. But few of them are fundamental, whereas I feel like if I bought a Rust book today, in five years it's a historical curiosity like my Stroustrup, except hopefully better written. I still consult my K&R a few times a year, I don't even know where the books I own on other languages (including the long obsolete Stroustrup) are, I might not have unpacked them after moving years ago.

If you take a look at the Rust book from five years ago and today, it's actually 40 pages slimmer (540 pages for the first version, 500 for the second) because most of the examples for some more advanced features Just Work without needing those features explicitly, and some other things got simplified. None of that stuff is wrong, and is still useful at times, but is used less often.

The core feel of Rust is very much the same today as it was then. Just things got smoother overall. We'll see in ten more years.

(This is on my mind, as we'll eventually be releasing an updated book for Rust 2021, at some point. Probably early 2022. It will grow in size again, mostly due to adding stuff about async/await, which is a major new addition to the language, but only needed in certain circumstances.)