Chess Opening Essentials by Stefan Djuric et al

4 volumes - Winner of the Italian Chess Federation’s Golden Award. 
These books are both primers and opening references that provide essential knowledge on all chess openings. The authors explain the basic plans and ideas for both sides in a way that will help develop a solid understanding of fundamental opening ideas. They explain the similarities with other openings as well as the differences and detail various middlegame plans that apply after the opening has ended.

Vol. 1 covers 1.e4

Vol. 2 covers 1.d4 d5 / 1.d4 various / Queen Gambits

Vol. 3 covers the Indian Defenses

Vol. 4 covers 1.c4 / 1.Nf3 / Other First Moves

All 4 volumes cover all main variations likely to arise and the use of color to highlight important moves and key positions is extremely helpful. Plans and counterplans for both Black and White are given in the form of simple, verbal prose and every opening is illustrated with a number of instructive games. Highly recommended for class tournament players wishing to improve. 

I would recommend that, after selecting what openings you want to play, you thoroughly review the material in the books then collect a database of master games with those openings. Play over them with a careful eye to how the games flow out of the openings and the types of endings that may develop. After you analyze 25 or so master games with your chosen opening you should have begun to develop a feel for how it should be played.

Books for Dummies

      I like these books for dummies. They don’t make you an expert in anything but what they will do is give you a good, simple overview of the subjects covered. This book is no different.        You won’t find masters using it, but if you are new to chess and want to learn opening basics or if you simply want to learn a new opening, Chess Openings for Dummies is a pretty good start. Disregard the hype that claims the book gives you tips and techniques for winning games from the very first move you make. That’s nonsense, but the claim that the book is a friendly, helpful guide that provides you with easy-to-follow and step-by-step instructions on the top opening strategies and gives you the tools you need to develop your own line of attack…that part is true.
      Some opening books like Modern Chess Openings feature variation after variation in column after column. My personal opinion is that MCO and books like it have outlived their usefulness. Other books specialize on specific openings or even variations and using them requires caution; some are good, some are downright bad. The nice thing about Chess Openings for Dummies is that it gives you a good overview of the openings you’ll most likely run into in practical play as well as good advice on what openings it makes sense for you to use in your own play. A big plus is Eade also gives you the ideas behind the openings and this is probably the most important part of the book. If you understand the ideas then, when your opponent deviates, you will have a basis on which to make a judgment as to the merits of his move.  You will also have some idea of how to take advantage of his move if it is not part of the correct overall strategy of the opening being played.
      All the major openings are covered and well organized: Open Games, Semi-Open Games, Closed Games, Semi-Closed Games and Flank openings are covered in depth in their own section. And…very important…there are the examples of master games played with the openings. This is vital because you really need to see complete games with each opening. Eade gives an example of when the opening is successful and when it isn’t. Highly recommended.