This book is about the relationship the constellation Orion has with the Pyramids of Giza. Mr Blauval and Mr Gilbert have written a fascinating book on the pyramids and what they were possibly used for. The Egyptology view has been the pyramids were built as resting chambers for the pharaohs of Egypt and nothing else. Mr Blauval has always had an interest in the Pyramids, and was originally from the area. He has an idea that the pyramids are aligned with Orion's Belt, and sets out to do the math and research to show the relationship.
There is much math and other measurements in the book, and the author goes on to show how the pyramids and a few other monuments do align to the stars. This book should be the starter point for the other books that follow and get more evidence to support the theories that the monuments of ancient times were a master plan. What that master plan happens to be is still up for discussion by the many other authors out there.
After reading this book, I would recommend "Fingerprints of the Gods" by Graham Hancock and "The Message of the Sphinx" by Robert Bauval and Graham Hancock (in that order). Those two books are good follow-ups to the theories presented in "The Orion Mystery".