I have a few which I believe might be of general interest, but am not sure about the copyright of some (wouldn't want to cause any legal fuss to AE).
Here is a list of what I have:
Charles Darwin - The Origins of the Species
Henry Smith Williams - A History of Science vols. 2, 3, 4 (you already have vol.1)
John H. Haaren - Famous Men of the Middle Ages
Rafael Sabatini - The Life of Cesare Borgia
Thomas Carlyle - History of Friedrich II of Prussia
Joseph Campbell - The Hero with a Thousand Faces
Carl von Clausewitz - On War
Francis Bacon - The New Atlantis
Thomas Hobbes - Leviathan
Mark Twain - On the Decay of the Art of Lying
Thomas More - Utopia
Adam Smith - The Wealth of Nations
John Maynard Keynes - The Economic Consequences of Peace
Carlton J. H. Hayes - A Political and Social History of Modern Europe vol.1
Frederich Schiller - The Thirty Years War
H.W.C. Davies - Medieval Europe
Robert F. Pennel - History of Rome from the Earliest Times Down to 476
Hutton Webster - Early European History
J. Fitzgerald Molloy - Royalty Restored, or London under Charles II
Ramsay Muir - The Expansion of Europe
Giancarlo Casale - The Ethnic Composition of Ottoman Ship Crews
Walter Pater - Studies on the History of the Renaissance
Phiip Schaff - History of the Christian Church vols. 1 to 6
Arthur Conan Doyle - The Great Boer War
Washington Irving - Chronicle of the Conquest of Granada
The Counter Inteligence Corps School - Counter Inteligence Corps History in World War II
Armgaard Karl Graves - The Secrets of the German War Office
Snorri Sturlson - Heimskringla or The Chronicle of the Kings of Norway
Nennius - History of the Britons
Jean Froissart - Chronicles
John Buffa - Travels through the Empire of Morocco
Lord Dunsany - Tales of War
Niccollo Machiavelli - On The Art of War
Niccollo Machiavelli - History of Florence and of the Affairs of Italy
Padre Lobo - Voyage to Abyssinia
Ramon Muntaner - Chronicle
Robert Kerr - A General History and Collection of Voyages vols. 1 and 2
James Ingram - The Anglo-Saxon Chronicle
Geoffroy de Villehardouin - Memoirs or Chronicle of The Fourth Crusade and the Conquest of Constantinople
Various Authors - The Complete Historic Court Memoirs of France
Unknown - The High History of the Holy Graal
And more. Especially literary fiction, but I don't suppose that has much interest here.