I'm not sure if people read books on the Alexander Technique anymore. The truth is that even if they're outdated, there's a tremendous opportunity for students to get ahead by learning from these books. If you're serious about developing a practice, then I recommend you start with the introductory books.

Also, books on the Alexander Technique have the most impact after you've studied for a little while, and are almost always confusing if you're brand new to the technique. If you haven't taken a lesson, then don't both reading a book...go for at least one lesson; it's best communicated experientially (like music).  Student's tell me reading helps with making sense of their experiences. That was (and continues to be) the case for me too. - Mark

Introductory Book(s):

The Alexander Technique: A Skill for Life  By Pedro de Alcantara

Body Learning: An introduction to the Alexander Technique By Michael J. Gelb (*The science/explanations are dated but still a good into read for students).

The Use of the Self By F.M. Alexander

Getting Nerdy Books:

The Body in Motion: It's Evolution and Design Ted Dimon

Freedom to Change: Development and Science of the Alexander Technique By Frank Pierce Jones

Directed Activities: A Diary of Practical Procedures for Students and Teachers of the F.M.Alexander Technique as Taught at the Constructive Teaching Centre (1989-1992) By Gerard Grennell

Even More Nerdy:

All other books by F.M Alexander

F.M.: The Life Of Frederick Matthias Alexander: Founder of the Alexander Technique By Michael Bloch

Directing and Ordering: A Discussion of Working on Yourself - Working on Breathing and Vocal Production By Joe Armstrong

AT Related:

Thinking Fast and Slow By Daniel Kahneman

Chair: Rethinking Body Culture And Design  By Galen Cranz

Awareness Through Movement By Moshe Feldenkrais

Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World By Christopher McDougall