I personally never really liked that book even when it was new. It's good if you wanna get up and running with JS fast while coming from another language, and are forced to use JS in places but it's not the main language of your project.

But it doesn't really give a strong foundation on understanding the language. It's more like "I know mainstream C-inspired languages, and JS often burns me with its weird quirks like how the this keyword works, I just want to avoid getting burned". But it doesn't really embrace JS itself, just sort of acknowledges that you will be forced to use it in the web so you may as well at least learn the "good" parts.

It's still decent at that purpose, but for really strong competency in JS I can also vouch for the Eloquent JS book and the You Don't Know JS series (I've only read the first edition, a new edition is partially complete and available online).