RMB & J.B. Bury 
The Dark Ages [EPUB ebook] 

The Dark Ages is a historical periodization traditionally referring to the Middle Ages, that asserts that a demographic, cultural, and economic deterioration occurred in Western Europe following the decline of the Roman Empire.
The term employs traditional light-versus-darkness imagery to contrast the era’s ‘darkness’ (lack of records) with earlier and later periods of ‘light’ (abundance of records).The concept of a ‘Dark Age’ originated in the 1330s with the Italian scholar Petrarch, who regarded the post-Roman centuries as ‘dark’ compared to the light of classical antiquity.
The Dark Ages Collection features:
HISTORY OF THE LATER ROMAN EMPIRE, by J.B. Bury
THE STORY OF THE GOTHS, by Henry Bradley
THE DARK AGES, by Charles Oman
VISIGOTHS PILLAGE ROME, by Edward Gibbon
HUNS INVADE THE EASTERN ROMAN EMPIRE; ATTILA DICTATES A TREATY OF PEACE, by Edward Gibbon
THE ENGLISH CONQUEST OF BRITAIN, by John Green & Charles Knight
ATTILA INVADES WESTERN EUROPE; BATTLE OF CHÂLONS, by Edward Creasy & Edward Gibbon
FOUNDATION OF VENICE, by Thomas Hodgkin & John Ruskin
CLOVIS FOUNDS THE KINGDOM OF THE FRANKS: IT BECOMES CHRISTIAN, by Francois Guizot
PUBLICATION OF THE JUSTINIAN CODE, by Edward Gibbon
AUGUSTINE’S MISSIONARY WORK IN ENGLAND, by Venerable Bede & John Green
THE HEGIRA; CAREER OF MAHOMET: THE KORAN: AND MAHOMETAN CREED, by Washington Irving & Simon Ockley
THE SARACEN CONQUEST OF SYRIA, by Simon Ockley
SARACENS CONQUER EGYPT; DESTRUCTION OF THE LIBRARY AT ALEXANDRIA, by Washington Irving
EVOLUTION OF THE DOGESHIP IN VENICE, by William Hazlitt
SARACENS IN SPAIN: BATTLE OF THE GUADALETE, by Ahmed ibn Mahomet Al-Makkari
BATTLE OF TOURS, by Edward Creasy
FOUNDING OF THE CARLOVINGIAN DYNASTY; PÉPIN THE SHORT USURPS THE FRANKISH CROWN, by Francois Guizot
CAREER OF CHARLEMAGNE, by Francois Guizot
EGBERT BECOMES KING OF THE ANGLO-SAXON HEPTARCHY, by David Hume