Cup and Cross tells the story of the Anabaptist movement. The author, Michael Martin, does an excellent job in differentiating between what he calls the faithful Anabaptists and the fringe Anabaptists. While the faithful are the true Anabaptists, the fringe element simply used some Anabaptist principles to advance their bizarre and destructive ends. Sadly, the fanatics have given the term "Anabaptist" a negative connotation.
The faithful in the movement took the Reformers' insistence on scriptural authority to its logical end point. They did not simply apply the bible to salvation but also to all of church life. This got the Anabaptists in hot water with basically everyone in positions of power in that society.
Cup and Cross is divided into two primary sections. First, Martin details Anabaptist history, focusing on the Swiss Brethren, Dutch Anabaptists, and the Hutterites. In part two, the author looks at Anabaptist beliefs. These include sections on scripture, the church, discipleship, and the state.
The only negative to this book is that the author makes some statements that call into question whether or not anyone outside of Anabaptism is actually part of the real church. He doesn't makes these statements about today but rather about the situation in Europe during the 1500s.
The Anabaptists are one of those groups that make us uncomfortable. The reason is that they lived out what they said they believed. Even in the face of immense persecution, they stuck to scripture for salvation, the church, the state, etc. They were not perfect, but they also did not shrink back in the face of great opposition.
This book is worth the read because it challenges us to ask whether or not we are living what we say we believe. If interested, read more about it here.