A large number of air cooled Volkswagen's used the Volkswagen type air cooled IV motor, such as 411's, 412's and '1972 and newer buses. The Porsche 912E and 914 used the Type IV also, but in fairness they are not technically "Volkswagens" but they are Volkswagen motors.
This book does not cover the type IV motor at all, and you wouldn't know it until you paid for it and read it.
So, it does not cover all air cooled Volkswagens as the name suggests, only the older bug/bus upright motors, and squarebacks.
So it's worthless to me since I have a 1974 air cooled Volkswagen bus with a type IV motor.
And as others have noted, it's quite outdated.