There is literally a Stack Overflow thread devoted to just about every single code example and paragraph in the book, because no one has any idea what he's talking about. And even the JavaScript gurus on SO can't figure out what he's actually trying to say a good percentage of the time.
I'm sure it would be a great book if I were already pretty good at JavaScript, but as a first book it's just awful. I had much better luck with a HeadFirst book that covered JavaScript, even though that is a little too dumbed down at times. I was then able to then go back and have a much better appreciation of what Crockford was trying to say.