This Brierley Guide to the Portuguese Camino came with me on my third pilgrimage. At the time, I knew nothing about the route from Portugal to Santiago de Compostela. As with its better-known sibling that covers the French route to Santiago, the heart of the book is the practical information. This includes daily distances, hill profiles, fountains, alternative routes, municipal albergues, and other places to stay. On the spiritual side, I enjoyed the history lessons and daily reflections on The Mystical Path, even if I didn't always follow them.
Caution: even with a guidebook, keep your head up and your eyes open. I somehow didn't see the huge sign for the Spiritual Variant (Camino Espiritual). As I result, I missed the boat. Literally.