TGP isn't a good book for learning JavaScript the first time, it's true.
The time to read it is when you've been doing this for a while, and it's time to "unlearn what you have learned" before you can move on to the next level of expertise. There's a lot of dogma in the book, but that's not bad in the appropriate context: most people will find something to follow in its pages, but most people will also find something to question. Both experiences are valuable, especially for someone preparing to "take the next step," as it were.
The time to read it is when you've been doing this for a while, and it's time to "unlearn what you have learned" before you can move on to the next level of expertise. There's a lot of dogma in the book, but that's not bad in the appropriate context: most people will find something to follow in its pages, but most people will also find something to question. Both experiences are valuable, especially for someone preparing to "take the next step," as it were.