International Master Al Horowitz goes through every major chess opening system and provides just one line of play for White, one line of play for Black, and the reason for each move by White or Black. This book will not show the reader how to win every game, but it will provide an easy route which will enable the player to get a reasonable, playable position out of the opening with good winning chances, even against the strongest opponents, without having to memorize a bunch of opening lines.
Because the reason for every move is given, it is entirely possible to learn every move in this book, simply by remembering the reason for the next move. Once the reason is remembered, then it is much easier to figure out what the next move is.
All of the lines in this book are still played at the top levels. None are obsolete. In addition, while some might consider them to be out of date, the average chess player does not need to know the latest theoretical variations. The old lines will do just as well, if not better.
This book is recommended for any tournament player rated below 1700. Players rated higher than that will probably already know most of the material in this book.