31 books
Wonders of the Mediterranean
The Art of War
The History of Medicine
Spies, Codes, and Secret Missions
Discovering the Age of Giants
The Age of the Greek Philosophers
The Period of Steam
Journey to Liberty
The History of Shipbuilding
The Dawn of Urbanization
The Great Era of Astronomy
Rivers of Influence
Chronicles of the High Seas
On the Trail of the Gold Mines
History's Fiercest Battles
The Early Empires
The Great Nile
The Mysterious Library of Alexandria
History's Greatest Feats
The First Human Settlements
The World's Oldest Stories
The Ocean's Greatest Mysteries
The Hidden Front
The Footsteps of Humanity