Publisher : Alfred Publishing Co., Inc.
This book is probably one of the best technique books available to the classical guitarist. It covers a number of topics including posture, the left hand (pressure, slurs, barres etc), the right hand (tone production, nail shape and length etc), the development of scale speed, and others.
I would -strongly- recommend this book to guitarists at all levels. Some of the pieces and exercises in the book will be too difficult for beginners and intermediate guitarists, but I would suggest just leaving these out until a more appropriate time - it is of more importance to read through the concepts he mentions and to try to apply them in your playing. Advanced level guitarists will also find the book useful, as it describes some very effective approaches to technique that you might not have used before.
There is also a video-cassette and DVD companion to this book, in which Tennant personally demonstrates the concepts in the book, as well as 2 companion books of supplementary exercises/pieces (one for Easy-Intermediate, the other for Intermediate-Advanced).