There are a very large number of books in English on the Alexander Technique and its application in various fields: music, running, swimming, horse riding etc.
My personal favourites as an introductory text are:
|- Body Learning
|- Alexander Technique
|- The Alexander Principle
|- The Alexander Technique, a skill for life
||Pedro de Alcantara
Alexander wrote an account of how the Technique originated which is worth reading.
|- The Use of the Self
||F M Alexander
The Society of Teachers of the Alexander Technique (UK), has a web page with details of available books and links to other sites. If you want to visit this site, please click here