I have read Keys to Progress, several times. Enjoyed it. The advice is simple and effective. I find it amazing that after 100000000000 variations on every program, known to God and man, the basics always prevail.
I agree with you on the 20 rep squats - I tried cycle of those not long ago and my old butt was hurting. Over and forty and twenty rep squats are a painful conbo-
The only rep that counts is the next one.