Recommended reads:

Audition by Michael Shurtleff

Michael Shurtleff has been casting director for Broadway shows like Chicago and Becket and for films like The Graduate and Jesus Christ Superstar. His legendary course on auditioning has launched hundreds of successful careers. Now in this book he tells the all-important how for all aspiring actors, from the beginning student of acting to the proven talent trying out for that chance-in-a-million role!
The Actor's Art and Craft by William Esper & Damon DiMarco

William Esper, one of the leading acting teachers of our time, explains and extends Sanford Meisner's legendary technique, offering a clear, concrete, step-by-step approach to becoming a truly creative actor. Esper worked closely with Meisner for seventeen years and has spent decades developing his famous program for actor's training. The Actor's Art and Craft vividly demonstrates that good training does not constrain actors' instincts--it frees them to create characters with truthful and compelling inner lives.
A Practical Handbook for the Actor by Melissa Bruder, Lee Michael Cohn, Madeleine Olnek, Nathaniel Pollack, Robert Previtio, Scott Zigler, and David Mamet

This simple and essential book about the craft of acting describes a technique developed and refined by the authors, all of them young actors, in their work with Pulitzer Prize-winning playwright David Mamet, actor William H. Macy, and director Gregory Mosher. A Practical Handbook for the Actor is written for any actor who has ever experienced the frustrations of acting classes that lacked clarity and objectivity, and that failed to provide a dependable set of tools. An actor's job, the authors state, is to "find a way to live truthfully under the imaginary circumstances of the play."
An Actor Prepares by Constantin Stanislavski

Constantin Stanislavski was an influential Russian theatre practitioner He was himself a highly-esteemed character actor and directed many successful productions. However, he is most famous for being the father of modern theatre and for his 'system' of learning to act, focusing on training, preparation, and technique. Concentrating on preparation, it offers the aspiring actor or actress tips and instructions on how they should prepare for performances.
The Empty Space by Peter Brook

The Empty Space is a timeless analysis of theatre from the most influential stage director of the twentieth century and co-founder of the Royal Shakespeare Company, Peter Brook.  Passionate, unconventional, and fascinating, this book shows how theatre defies rules, builds and shatters illusions, and creates lasting memories for its audience.
Moment Work: Tectonic Theater Project's Process of Devising Theater by Moises Kaufman and Barabara Pitts McAdams

For more than two decades, the members of Tectonic Theater Project have been rigorously experimenting with the process of theatrical creation. Here they set forth a detailed manual of their devising method and a thorough chronicle of how they wrote some of their best-known works. This book is for all theater artists--actors, writers, designers, and directors--who wish to create work that embraces the unbridled potential of the stage.