My opinion is that at this point you wouldn't read JavaScript: The Good Parts to become more effective with the language (the books original intent).
Modern JavaScript is substantially different from what's illustrated in that book both in terms of language design and popular style. The ecosystem built around the web has moved on as well. Very few programmers spend their day manually manipulating the DOM anymore - almost always there's a library in between doing that.
The reason I _would_ recommend JavaScript: The Good Parts to someone is that it's one of the best examples of a well written technical book that I'm aware of. It's at once clear, deep, and concise. It's an easy read that assumes very little in terms of the reader's prior knowledge.
So many technical books are frankly very poorly written but Crockford, whatever you think of him, is exceptionally gifted at illustrating technical topics in a way that is easy to understand.