No need to read the manual to understand what is happening is right with the ears (provided they are flexible enough lol)
Connected between my Gretsch Electromatic hollow-body and my Fender Blues Junior, I used to light cruncher. The color is quite transparent and does not alter at all my basic sound, bass and treble settings do not allow "Scult" sound but to correct it by finesse (for my part I decline a bit high).
By lowering the drive it can be used to boost, it's clean and dynamic sound. However when you push the drive back to a distortion gives a little stiff as I was not convinced it is better to stay in the crunch.
If you find an overdrive to use a Tube Screamer type but without the pervasive mediums (sorry for the fans of the TS ...) and with a little less drive. This is perfect for blues, especially if you have a good amp, the mystic swells and twists your signal without distorting it. It is perfect to boost an already present disto. Its only flaw is that it will not radically change the sound and it is interresting that if you have a good basic sound.