This is the second book on Egypt that I have read by Robert Bauval. I would recommend reading the first, The Orion Mystery, before starting this as it occassionally references back to topics written there, and I found it very helpful to have the background on the pyramids discussed in The Orion Mystry.
The Message of the Sphinx moves away from the Great Pyramids a bit and centers on the meaning, purpose and age of the Great Sphinx. Newer theories (1996) suggest that the Sphinx is much older than originally thought and also suggest a new purpose for the anciet monument. These discoveries are based in science and lead to a very compelling argument for the writers' theories.
If you are interested in Egyptology, this book should be on your must read book. Even if we choose not to believe the authors' theories, it shows a new picture of the ancients that helps piece together how and when they lived, specifically their religion and funeral rites. The writing gets a littel overly scientific for easy reading so I've been picking it up on and off all year.