Jim is outside the Rust project, other than working for the same employer as many of the Rust developers.

And I think pcwalton is saying that Jim Blandy is very much from outside the Rust project, and therefore satisfies that criterion. :)

Then I guess the OP had another definition of "book" in mind. However, I'll say this: if Jim wants to write a complete book on Rust, I'd love to buy it. I'm more than halfway through his report and it has exactly the tone that I'm looking for in a programming book: clear, logical progression, to the point and no excessive humour that some books suffer from (I'm reading a book on Go (the game) at the moment and every paragraph contains a self-deprecating joke. It gets old after 2 or 3.)

To expand on steveklabnik's sibling comment, Jim Blandy's is writing a complete book on Rust, which will be published by O'Reilly, and is aiming for release by the end of the year. :)