Here are several free e-Books on the Protestant Reformation made available by our friends at monergism.com:
History of the Reformation of the Sixteenth Century
by J. H. Merle D’Aubigne
The Necessity of Reforming the Church
by John Calvin
Life of Martin Luther
by Joel R Beeke
The Reformers and the Theology of the Reformation
by William Cunningham
Historical Theology
by William Cunningham
Dawn of the Reformation
by Herbert B Workman
William Farel: The Story of the Swiss Reformation
by Earl M Blackburn