The cue ball and the next ball are kissing. If they are pointed at a diamond and you want the cue ball to hit another ball next to the pocket, you split the difference and hit the cue ball at the midway point. The cue ball is supposed to pocket the ball into the pocket. I've found there are only a few places where this works and maybe that is what Ray meant.
Shot 42 is almost a description of the "two times fuller" system. Here is the page from "99 Critical Shots":
Prarie Dog is correct. If you specify the distances like that, the shot will usually not work. The shot as described will work only if the cue ball/blocker point nearly straight at the correct cushion.
An example of where the shot goes wrong: Turn the pair in the diagram counterclockwise until they point at the top side pocket. The system for Shot 42 then says to shoot the cue ball at the diamond two diamonds from the side pocket and two diamonds from the target ball. That is completely broken.
For me the main problem with the book is the size of the balls -- like basketballs. I prefer to have diagrams drawn to scale. I think then they are much easier to understand. I'm disappointed that they were not redrawn for the 30th anniversary edition.