It's usually used in conjunction with the NEC book.
If you have to understand a book the NEC is the one you're expected to perform to.
Ever read it?
IIRC, The Electrician's Handbook
is for Canada. The American Electrician's Handbook
is for the US. I've read neither cover-to-cover.
Being a licensed electrician in NJ just means that they passed a test that uses many questions that are NEC based.
Being an electrician in most US jurisdictions means more than a nodding familiarity with the NEC. There are a few that don't adopt the NEC but they're few and far between.