Books and teaching packing are tough. Pretty hard to understand rope knots in words on hitches unless you are already pretty experienced with the basic packing knowledge. I taught packing for 5 years along with Cody and LeRee of Royal Tine guide school. They have been teaching it for over 30 years, and run multiple 4 day weekender clinics during the summer that ive sent numerous people to and all have been very impressed with how much they take away from a short course. Aside from going to one in person, they created a great dvd that goes over all aspects of backcountry horsemanship and packing, and might be a little easier to understand than reading a book about it. https://www.royaltine.com/courses/instructional-packing-video/