I have purchased it and it's pretty good. Although it really seems to be geared more towards experienced systems programmers. The online book is much better for beginners, IMO.
And The Rust Programming Language (https://doc.rust-lang.org/book) is on its way to paper publication.
The newly minted Rustonomicon (https://doc.rust-lang.org/nightly/nomicon/) that covers deeper aspects of Rust is hopefully destined for the same.
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