J. B. Bury 
The Invasion of Europe by the Barbarians [EPUB ebook] 

J. B. Bury was an Irish historian, classical scholar, Medieval Roman historian and philologist. He objected to the label ‘Byzantinist’ explicitly in the preface to the 1889 edition of his Later Roman Empire.In print for more than thirty years, this book has long served as a standard text on the Germanic penetration of the Roman Empire. Bury’s history is indispensable to anyone who seeks to understand the connection between the barbarian migrations of the third to the ninth century and the framework of modern Europe.