H. A. L. Fisher 
The Republican Tradition in Europe [PDF ebook] 

First published in 1911, this pioneering and ambitious work provides a history of the evolution of republican thought and practice in Europe from the fall of the Roman Empire to the beginning of the twentieth century.

Based a series of lectures delivered by the author at Lowell Institute in 1910, this is a comprehensive treatment of the subject which moves deftly from the political thought of the middle ages through to the rise of Protestantism, the wave of revolution across Europe in the eighteenth and nineteenth centuries, concluding with an analysis of the republican cause and the permanence of the Republican idea in the consciousness of Europe.