This might've been a very helpful book 12 years ago, but a lot has happened since. Heaps of researches have made their debuts since then that seriously outdates this book... by 12 years.
For example, the author's list of ADD symptoms only covers the hyperactivity element and neglects the symptoms of a child with inattentive type ADD (without hyperactivity). An inattentive type wouldn't necessarily have a hard time sitting down. Contrary to many of the items on the list, a child with inattentive type ADD would more likely be day-dreaming (similar to being hyperactive in one's own mind.. as I'd like to think of it).
Try to stay away from this one.. (unless if you're writing a paper or something and need to comepare differences/similarities between what we USED think and what we know/think NOW.)