Not just, "these are forks, pins, skewers, discovered and double attacks," but also, "here are situations where /escape/ is possible from such multiple threats." 438 find-the-successful-attack-or-defense positions, 4 per page, with answers & explanation. 1973.
If you want to be competitive in chess then you have to go beyond strategy. Strategy is necessary to be a good player but so is tactics. This book contains 438 different situations, four per page, with answers at the bottom. Great practice. Forks, pinning, skewers, defense, check mates, etc. It assumes you already know the rules of the game. It is marketed as a book for beginners but many have said, including me, that it is also helpful for the seasoned player. I got a lot out of it, and I feel I am a better chess player as a result of doing every exercise in the book.