Each volume of Counsel Quick contains different information. There is no overlap in material between volumes. The general rule of thumb is that Volume 1 is geared towards first line leaders. Volume 2 is geared towards more senior leaders. Volume 3 covers sort of a mixed bag of counseling subjects we felt were missing from the first two.
If you are a first-time counselor and just looking to get your feet wet, Counsel Quick Volume 1 covers the basics and will give you a great place to start.
You can see which counseling subjects are covered by the various volumes by visiting the Counsel Quick page. There is a by-subject comparison of all three volumes near the bottom of the page.