I'm no enthusiast for nothing (don't tell my wife! :-). I find the authors approach very convincing, and his self-praising very annoying. The 10 levels of each exercise allows a comfortable entry for everybody. Calisthenics in addition is very cheap.

I'm training for 3 weeks, on level 1 to 6, depending on the exercise, and I feel a lot fitter and happier.

I made my own training plan, traing just every second day.

I'm old, so progression ist not fast, but I have no interest in that. If I'm on level 10 in every exercise in 10 years, I will be very happy.