I found this book when looking for something above the many "basic" presentation skills books that are out there - and this book delivers.
Ralph covers the various voice qualities in detail, and the impact these qualities has on audience perception. He covers how to add more variety to your voice via rate, pitch and volume - each are covered in detail along with when to vary these for effect.
Ralph also covers how to support your voice, and then goes into the technical aspects of voice production and phonetics (via the International Phonetic Alphabet - or IPA).
The book finishes with tips on dress, movement, eye contact, external factors, health and practice. It also includes 27 exercises designed to improve your voice and overall presentation technique.
Overall this book provides much information that can help take your presentation style to the next level.