"What, in the I opinion, is Gadalla's most important work?"

I have read six of his books and none of them had much to do with pre-dynastic Egypt. He, like most Eurocentric Egyptologists, focuses on Egypt at the Apex of her civilization or when she comes into contact with foreign invading forces.

As an engineer, his value lies in his ability to align ancient Egyptian wisdom with 20th and 21st century scientific thought. I recommend "Egyptian Harmony-The Visual Music."