A billiards theory book that answers your questions about 3-cushion billiards.
Vol. 1 is a theory and system section, and covers the basics of billiards, including the origin and history of billiards, types of billiards, billiard etiquette, rules, posture, alignment, hitting, and laws of physics, as well as the fundamentals of billiards, variable English system, fixed English system, spread system, and isometric system.
It also contains new techniques that the author himself created, and has inserted illustrations here and there to help readers understand more easily.