He Shall Thunder in the Sky, by Elizabeth Peters
This is the twelfth book in the Amelia Peabody series. In this book, they return to Egypt for another excavation, but little of the book sees any archaeology work. World War I is raging, and events engulf our heros in intrigue and mystery. The Master Criminal is back, and has placed himself in the center of affairs.
As it goes with the series, this book is more about the characters than the events. The main characters continue in their unusual styles to entertain us. Ramses and Nefret are maturing in more ways than one, and insert themselves into the intrigue that surrounds them. As events play out, we learn new and unexpected events and histories of several characters, including the past of The Master Criminal.
This book was better than several of the preceeding ones and is worth the read. This book would stand on its own, except that the reader would lack a good understanding of the characters which provides most of the value of the book.