I have just completed a two week visit to the battlefield sites of northern France and southern Belgium. This particular Holts' guide is one of a pair covering the region that we used (and I understand there is a separate tome on the Somme itself), and has a tremendous amount of detail. The maps and illustrations are excellent, and the guide is very comprehensive, with a personal touch provided by the comments of Major and Mrs. Holt.
While very comprehensive, I must admit to finding this guide difficult at times to extract the appropriate information from. This is probably because I simply didn't have the time to spend reading it before setting off on our trip, but the problem comes from the difficulty in combining chronological and geographical history. The static nature of the conflict on the western front meant that events in time happened on the same sites, while the expanse over which the conflict took place saw offensives on a single date occur over a great distance. The reality is probably very difficult to reconcile, no matter how you divide a guide book, and the Holts' guide probably does it better than others, but I still found it difficult to draw the two competing factors into one clear, comprehensive understanding of the events of this most tragic episode. This limits the ease with which the guide may be "dipped into" for details on some sites and events.
Overall, these comments reflect the difficulties of the situation, and the Holts' guide is probably as good as could be imagined. However, I would strongly recommend some prior research and reading from the guides before embarking on a tour of sites, as I am sure familiarity would help in relating the guide's information to the events and locales described.