There are only a few books that can be hailed as "a must for a piano pedagogue."
Heinrich Neuhaus, "On the art of piano playing"
Gieseking, "Piano Technique..."
Josef Lhevinne, "Piano..." (sorry, I don't remember the title, but it is the only one he wrote)
All three differ in style, but they have one in common: the authours were the three greatest pianists of the last century. Neuhaus, on top of that, was a terrific literary talent, and his book is the place where great subject meets great writing. Has it been translated? This book has been the Holy Writ of all Russian pianists.
Lhevinne's book is the shortest and the most comprehensive. It is uncanny that everthing a pianist must know about the mechanics of piano playing is given in a concentrated form in this book. Its English is not idiomatic; yet, it goes well with the whole "Russian school" thing.
The Leimer-Gieseking book is an attempt at presenting a philosophy behind their science. It is written in a heavy German style, which means you can read every other page and still get the point. The whole book can be formulated in a few short sentences, but a German-born and bred writer would never commit such a sacrilegious act ("leave it to the Russian barbarians..."). Namely, "practice with your head, not fingers; develop your inner hearing; study your scores mentally, not at the piano; cultivate your imagination of the sound-picture; visualize the physical act of playing, complementing the mental picture with a full-blooded image of the sound."
Still, READ THE BOOK, there is no excuse for being under-educated.