I've listed seven federal publications that were of great help in my learning forestry and explaining the practice of forestry and silvics to others. These booklets are well written, offer information that is often hard to find and are all free as online downloads .
You may have experienced sticker shock after purchasing technical forestry books. You will find these "gems" well worth the investment of time and effort to acquire. Again, all are available for free to view online and bound copies are available from several sources.