Portier's Divided Friends is a must read for anyone interested in the history of the Roman Catholic Americanist and modernist controversies, and anyone interested in the history of Catholicism in the U.S. In the past scholars have considered the Modernist controversy to be a wholly European affair. Scholars will no longer be able to ignore the impact of the Modernist controversy on Catholicism across the Atlantic in the U.S. Portier's volume marvellously captures "the human complexities" (p. 5) involved in the modernist crisis. He is able to do this because of his tremendous erudition and his thorough archival research. The biographical stories he includes paint vivid portraits of the lives of four priests who struggled with issues concerning faith and reason; two continued to serve as Catholic priests, two left the priesthood and the Catholic faith. By examining their biographies prior to, during, and after the crisis, Portier is able to show the ways in which the modernist crisis was related to the Americanist controversy which preceded it. The many controversies emerging in late nineteenth and earlty twentieth century Catholicism are incredibly complex, involving far more than only theological and philosophical matters, and they include polyvalent political dimensions. In Divided Friends, Portier eschews overly simplistic polemics, and instead offers a thick, nuanced, and rich analysis of the history. Despite the many complexities involved in this story, Portier's prose is lucid and engaging. I would highly recommend this book for use in the classroom, especially in graduate and doctoral seminars, but also in specialized undergraduate courses that relate to the history of Catholicism on U.S. soil, and particularly any courses dealing with the Catholic modernist or Americanist controversies. Divided Friends is essential reading for scholars interested in modernism and Americanism, but would also be of interest for non-specialists. Any educated reader who is interested in the topics covered will find in Divided Friends a book well-worth reading.