I haven't read this whole book cover to cover, because of time constraints. However, I can say that it is extremely clear in it's exposition. The material is very well chosen for use by physicists. I have read pure math books on this topic, and while they can be more sophisticated and thorough, they are rarely as straight forward, nor do they cover the breadth of material in this book.
In sum I would have to agree with what I was told: "this is the book on Lie Algebra for a physicist".