One of the best books on this topic is Free Throw: 7 Steps to Success at the Free Throw Line by Tom Amberry
While it is specifically about free throw shooting, the mental aspects are almost exactly what archers do.
Another very good one is Instinctive Archery Insights by Dr Jay Kidwell. Dr Kidwell often posts here. His username is J-kid.
IMHO mental training and techniques are useful for those archers who have mastered the physical techniques and skills of archery. In fact at the highest levels of competitive archery, such as the Olympics, the mental skills may be the only thing separating one archer from the other.
I don't think that mental skills help a beginning archer very much. He has to learn the physical part first.