It is very difficult to be judgmental about this book. Generations of Indians learnt their grammar from this book (take what you will from that statement:) ) There were two versions of this particular book and I remember I used to have the green cover one. Plus I think there was a middle course in Red. For a lot of us who studied in the late 80s and 90s this was the go-to book for grammar. Since one could get full marks in grammar and since getting marks was the most important part of our study process we really lapped up this book from end to end.
I had a quick look at the book and find it still relevant especially the parts defining the structure of the language. I guess the fundamentals of grammar will never change.