This guy is a seminal martial arts teacher.
I have purist martial arts expert buddies who sneer at him because his technique isn't the same as the technique taught in their styles. Or because he doesn't teach obviously vicious and death-dealing techniques.
Well, too bad!
What they don't understand is that Tegner was writing to a civilian population in a relatively safe, law abiding world, where most guys were going to deal, at worst, with some bullying and a challenge to "take it outside". He was not, in this book, preparing guys to be commandos or inner-city cops.
Tegner knew that most of the people who read his books were not going to spend ten or twenty years in a dojo learning techniques that had only some application to the real world.
Tegner was a serious judo guy. He'd studied all his life. And judo guys aren't sissies; they call it the gentle way, but when a judo guy hits you with the biggest weapon around (the planet Earth) it doesn't feel very gentle. And you can get seriously hurt in judo if you aren't lucky.
He'd also studied broadly, and had a good knowledge of what techniques were available for hand to hand combat of all sorts.
He made intelligent choices in techniques that laymen without a lot of time or energy to spend on training could practice some and improve their chances of surviving a fight.
If you are a beginner to martial arts and want to read an author who has balanced ease of study, length of practice, and likelihood that the techniques will send you to Sing Sing after the fistfight, this is a perfectly good place to start.
Bear in mind that no book can teach you to fight, and that you'll need to practice with a partner and on a bag. Also bear in mind that the laws of self defense differ from one to another jurisdiction.
In any case, buying all the Tegner books there are and reviewing the sorts of tricks he teaches is a perfectly good way to begin a study of self defense.
And I give this guy five stars partly because of the cost to technique ratio!