Gonzales was King
For five years running, Pancho Gonzales was the premier player in the world, and among the top ten for years thereafter. The only reason he didn't win as many Grand Slams as those who followed was that, as the leading amateur, he turned professional at 19 to play Jack Kramer on Bobby Riggs' national tour and was too old by the time the Open era arrived (when professionals became eligible to participate). He had the best serve in the world, and only Lew Hoad of Australia could stand up to him (on a given, rare occasion). Anything and everything Gonzales tells you, you can "take to the bank" to improve your game. His earlier book "Tennis", authored with the help of Dick Hawk, is also highly recommended.