Private lessons are extremely valuable, and individual practice is crucial to success. There is another layer of personal study that involves reading about one's discipline to be more informed. There is a great body of literature for any field, and becoming aware of the history and best practices of what we do is vital. After all, I remember Tim Hudson saying that everyone basically teaching the same things, just in different ways. While there certainly exists poor pedagogy and unhelpful literature, a basic search and query of current professionals can lead one to finding a helpful body of literature to process.
This aspect of study is crucial. However, certain books are more helpful in different stages of development than others. For example, one has learn to be objective when reading books that address many physical problems or specific techniques of playing. There is a certain level of maturity required to avoid taking in too many problems as our own. Keith Johnson addresses this in The Art of Trumpet Playing, and Phil Farkas does as well in The Art of Brass Playing. A personal example is The Inner game of Tennis, I had not been introduced to sports psychology, and this book was too dense for me when I started it. After reading other books such as Golf is not a Game of Perfect by Bob Rotella or Audition Success by Don Greene, coming back to Gallwey's book on tennis was more appropriate for me developmentally. Be intentional when suggesting books to young players, and picking books for yourself. Information is needed, but it is most helpful at the developmentally appropriate time.
Time to keep exploring,
Adam C White