GM John Emms wrote an introduction to basic opening principles, Discovering Chess Openings (2006).
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf
"Throughout the book Emms uses excellently chosen examples to expand the readers understanding of both openings and chess in general. Thus equipped the student can carry this knowledge forward to study individual openings and build an opening repertoire.
Books of this kind in relation to openings are quite rare – and good ones even rarer. For beginning players, this book will offer an opportunity to start out on the right foot and really get a feel for what is happening on the board." - FM Carsten Hansen (2006)
ex_submariner wrote (~5 months ago):
"If you can find a copy of 'How to Open a Chess Game', buy it! Published in 1974 there are seven chapters, each by a leading grandmaster of the day ... The chapter 'Developing an Opening Repertoire' by Lajos Portisch alone is worth the price of the book. ..."
"... For white kingside openings Portisch recommended the Ruy Lopez exchange variation. ... For closed games as white he said play the King's Indian Attack and the English Opening. Also the QGD. ..."