Although nearly twenty years old, this is the book I would most recommend to students, actors and voice tutors.
What I like best is her discussion of the right to speak and how to go about it in any walk of life where public speaking is required. She is very good at analysing fears about speaking in front of an audience.
You have to work with this book both in thinking along with the first section and how it applies to you, and going through the exercises in the second part. She makes the self analysis much easier than writers of other books in this genre, and the self-teacher can check their strengths, weaknesses and progress without too much effort.
Teachers of Speech and Drama should have this book constantly to hand, as it covers essential areas of voice and speech in performance that a trainee performer needs, but which are often covered in insufficient detail in board syllabi.
Not only are the exercises comprehensive and useful, but there are also ideas on the development of their usage with specific texts and acting situations.
I cannot recommend this book highly enough. It is sure to be a few years yet before it is superseded.