Michael Hoffman writes an engaging and informative book of the discoveries and the discoverers of Egypt before the Pharaohs.
Originally written in 1979, even without the latest findings of the last 25 or so years, it is well worth reading for the personalities and excavation details so often omitted in more recent works. 
This book is nearly 40 years old, but it is still probably the most thorough description of Predynastic Egypt. The study of Egyptian prehistory progressed sluggishly and was weighed down by outdated ideas during the middle of the 20th century. Hoffman wrote after a wave of discoveries and new thinking transformed scholars' picture of the subject into something not very different from that of today. Hoffman's book examines the whole sweep of time from Paleolithic Egypt to the unification of Egypt, with a postscript on Khasekhemwy, a Second Dynasty ruler, as a symbol of the emergence of the sophisticated Egyptian state.
Hoffman's versatility is impressive. He interweaves his story of how Predynastic Egypt developed with the history of how Egyptologists studied the period, which is interesting but may be a little hard for some readers to follow. Our understanding of the Predynastic leans heavily on the evidence from Upper Egypt from Abydos to Hierakonpolis, and that was still more true when Hoffman was writing than it is today. Yet, as much as was possible in 1979, he examines the widely different regions of Egypt, from the Delta to Nubia, and how each environment shaped the development of the societies there. He also compares Predynastic Egypt to other cultures across the world to understand the processes that formed it. He thus brings in a breadth of anthropological ideas that are rarely found in Egyptology, but they're from the 1970s, and our understanding of early civilizations and state formation has changed a lot since then. It's in this area that Hoffman's work is most likely to be outdated, though yet valuable and absolutely useful.
if you are into Egyptology, especially before the Pharaohnic era, this is a must have book!