Oh the misery of some of the other comments here. This is a fine piece of work.
I've been working with JavaScript on and off for years (though am far from an expert), but something like this is still a great primer for me, even the introductory stuff. It never hurts to retread the basics quickly and from the perspective of someone you know is a seriously expert developer right NOW (and not when I picked up most of my JS.. 7-8 years ago!)
Forgetting that, what I've read of it so far is well written and not padded to fill a certain page count like many books. It's open, it's free, and even if it's not going to win any prizes, it's certainly way above average in the gamut of programming books, free or not.
I'll add two cents: as someone very new to JavaScript, I like the idea of a rapid introduction to the language and then straight into jQuery (which I would expect to use more than "raw" JS for the near future anyhow).
Also, putting the book on GitHub was genius. There are already 13 forks, and the author has been very quick to respond to issues posted there. (Full disclosure - one of the forks is mine. I can't contribute to the jQuery part, but I tried to help out with the installer script when the author mentioned it was a bit wonky.) Releasing a book in this way allows people to add value (if they can), and it's great to see an innovative use of GitHub. (There may be lots of other books available there, but it's new to me if so.)
I've been working with JavaScript on and off for years (though am far from an expert), but something like this is still a great primer for me, even the introductory stuff. It never hurts to retread the basics quickly and from the perspective of someone you know is a seriously expert developer right NOW (and not when I picked up most of my JS.. 7-8 years ago!)
Forgetting that, what I've read of it so far is well written and not padded to fill a certain page count like many books. It's open, it's free, and even if it's not going to win any prizes, it's certainly way above average in the gamut of programming books, free or not.