I was coached by Jack in college. I found him to be a wealth of knowledge if only you asked him. He is a quiet, contemplative man who, often, will only provide his input/opinion when it is asked for. To this day, I don't know why he coached Div.III when he could have coached virtually anywhere in the country though. Whilst I didn't run that well in college under him (mostly due to injuries and hangovers), I learned an immense amount.
Part of the reason I went to Cortland was not to be a great runner (I am realistic), but to lay the foundations of being a great coach (a more achievable goal, I felt).
His book explains in 'plain English' some tricky physiological stuff that other books (e.g. Martun & Coe) treat as if you are in a grad-level Ex.Phys class. Daniels' book is far more user-friendly and readable.
I would recommend the book to any aspiring runner, especially marathoners. He recently told me he is working on a new edition of DRF.