I'm just back from walking all 800km of the Camino Francés from St Jean to Santiago. This book was indispensable - by far the most helpful for my daily journey, and in giving me a good list of things which were necessary before I started. It also had a very useful list of some of the more common things I would have to say/ask for in Spanish. Two aspects of the book were exceptionally helpful: the maps and the historical notes.
Brierley's maps are clear and concise and give you an excellent idea of the walk ahead of you each morning. His historical notes were extremely helpful, especially when you bear in mind that there are some 1800 historical sites along the Camino Francés. His notes on churches, battles, historical developments and so much else gave me at any rate a greater comfort and sense of continuous education along the walk. Other observations, such as the types of crop grown on the Meseta Central in contrast to the lowlands, increased my knowledge of farming life in these parts of Spain. His overview map of all 33 stages in the first three pages was particularly useful, while his guide to the hostels on each day's journey was most helpful.
Now for the weak points. They were very minor in comparison. First, you may not take to Brierley's spiritual notes and personal reflections. I didn't but you just overlook them so it isn't an issue. Second, which was the relatively more serious issue, Brierley's book could be improved for the last 100-odd km from Sarria. Specifically, there are a number of new cafés/restaurants along the camino which do not get a mention and this posed me some difficulty in determining whether I had gone the correct way (the waymarking was weak around the area I'm thinking of). In absolute fairness to Brierley, however, he notes in the book that there is a quite rapid expansion of such cafés along the camino every year and these places looked new. There were also other anomalies such as on Map 28 (Triacastella to Sarria via Samos)the map clearly shows you go downhill when you come out of Triacastella but in reality I had a fairly steep climb up the asphalt road to Samos immediately when I left Triacastella.
However, on other occasions, particularly at the start, I was sure he was wrong and it ended up that he was correct and ultimately put me on the right track. One other thing, he has great information on the different routes to each place - e.g. the recommended route, alternative route etc - and this allows you to plan each day's trip according to your level of fitness and time constraints. Overall, this is well worth getting and, judging by the number of English speakers who were using it, it has now become the standard guide on the camino. It's small, yet bursting with relevant information.