Kyle Simpson's books.
His books transformed my understanding of Javascript. He basically bursted into the chest of Javascript, grabbed its beating heart, and then pulled it out and showed me (just like in "Indiana Jones and the Temple of Doom").
His series "You Don't Know JS" gives you a profound understanding of the language. It really teaches you why JS does all of the weird things it does.
I wasted a lot of time by not reading those books earlier.