An excellent overview of the historical, cultural, religious, and artistic elements of the Camino de Santiago. I carried this book during my month-long pilgrimage, and it was well worth the weight.
Reading this book while on the Way of St. James is like having two immensely knowledgable tour guides at your side at virtually every noteworthy location on the trail. Both authors are professors of Hispanic studies at the University of Road Island, and their encyclopedic knowledge of Medieval northern Spain is both insightful and captivating.
The book is intended to supplement a travel guide; it does not speak of places to eat, sleep, or schedules of churches or monuments. It more than makes up for this lack of practical travel advice, however, with history, folklore, lives of saints, and cultural observations that make even the most seemingly unremarkable landscape come alive.
If you are contemplating completing the Camino, I would highly recommend this book, some spiritual reading (I read St. Ignatius of Loyola's Spiritual Exercises), and an up to date guidebook that includes maps of the trail each day and recommendations on albergues, restaurants, and schedules for points of interest.