By “official”, I think you mean “written by the people responsible for JavaScript”.
Just speculating here really, but the people responsible for JavaScript (the ECMA) don’t directly make any money out of it, and probably don’t have any particular skills in writing reference documentation. So they have neither the incentive nor the ability to write a good reference.
Personally, I like JavaScript: the Definitive Guide from O’Reilly. There’s a sixth edition coming out in November.
