I'll begin by saying that I did, indeed, read the entire book! I think this book is essential reading for anyone who diagnoses ADHD. I'm a clinician myself, married to a surgeon. We both feel strongly that ADHD has become a catch-all diagnosis from unqualified clinicians, who don't take the time for a differential diagnosis, or make the referrals that should be required!
While I believe that Dr. Saul's theory (see the title) is just that, "his theory," there is important information here.
When I first read of ADD, in 1982, I had no interest in treating it, as I'd learned to deal with it for 30 years. In my fifties, however, I had a sense that menopause exacerbated the symptoms. I saw an expert, who concurred, and I began taking Adderall, 10 mg, timed-release.
The medication has been a godsend for me. Perhaps Dr. Saul would diagnose me as having neurochemical distractibility/impulsivity, but I don't care what it's called. For me, Adderall works.