The Radar Book is a good text for someone who hasn't had any experience at all with radar. But as Sea says, it's getting a bit dated in terms of the technology unless the book has been updated recently.
As to using 0.125, 0.25 and 0.50, I agree that running with that range as the constant setting is kind of unproductive and could be dangerous. However, one of the first things I learned about radar years ago from the captain of the Matsonia, a 600-foot roll-on/roll off ship I rode and filmed on from Oakland to Hawaii, is that it is not a "static" instrument. It's an instrument that is most valuable when it's being "played" by an operator. (This was the captain's analogy which I've never forgotten.)
When we run in fog, one of us drives and the other one operates the radar. The position of the display in our boat is such that both the helmsman and the radar person can see the display.
Depending on the location and situation, we are frequently changing the range and changing the gain. This give us the big picture as well as the close-in picture, and changing the gain gives see things like crab pot floats right in front of the boat and then targets that are farther away in a less-cluttered view.
In a narrow passage that may be only a few hundred yards wide, running at anything over 0.125 or 0.250 makes the passage so tiny on the display that picking out targets in the passage is difficult to impossible.
We run our radar all the time regardless of the visibility. Even in good visibility we "practice" the technique of changing range and gain, comparing what we see on the display to what we see out the window, and we'll often use the bearing and range lines to track other vessels just to stay current on the procedures.
