Its a map - yawn. It is however very useful if you are completing the CTC and well featured. Having completed the ride a couple of times I heartily disagree with at least one element of the relief map and I believe that more explanation is required of some alternative routes. Hence 4 stars. Otherwise this map will direct you reasonably adequately from point A to point B.
This map is the must-have map if you do C2C. Surface condition, alternative routes, bike shops on the routes, altitude, and etc, everything you need to know during the trip is on this map. This also comes with a plastic transparent cover so you can quickly check the map even on a rainy day.
Although the C2C route is well signposted, the map is also useful for general planning, mileage calculations and alternative routes. In my opinion, best used in conjunction with a more descriptive book, such as The Ultimate C2C Guide.