Here are some books that are on my shelf and about acting.
1. The Actor and the Target by Declan Donnelan - author is the artistic director of England's Cheek by Jowl, and this book is his ideas about what acting is, based on the idea of getting around what is 'blocking' an actor.
2. The Viewpoints Book by Anne Bogart and Tina Landau, A Director Prepares by Anne Bogart, And then, You Act by Anne Bogart - the first book has more of a workbook quality, and outlines the technique of Viewpoints. The other two books are more collections of essays by Anne and her ideas about making theater.
3. Actions: The Actors' Thesaurus by Marina Calderone and Maggie Lloyd-Williams is a slim volume filled w/playable verbs, and synonyms for those verbs. If you are the type of actor or director who likes to think about playable actions when analyzing text, then this book is indispensable, I'd think.