Top positive review
Great guide, highly recommended
3 December 2017
Used it on my recent trip doing the full GR20. Some useful information for planning the route and the route descriptions were helpful both in terms of getting an idea of what the day ahead would be like and in helping us get back on track when we missed a marker and continued briefly in the wrong direction. The markers are so frequent you shouldn't get too far off the path before you notice, but when reading the route description take note of when it says "watch carefully for the..." as it probably means there'll be a sharp turn and you do actually need to watch carefully for the markers to not miss it! If you understand French there's another commonly used French guide which has topo maps included which could be nice to have, but you don't need them. We took print outs of the free downloaded topo maps and never used them, even when doing some of the common sides trips.
Main downside to the guide is that information on going out of season is very limited (including on huts/supplies/transport/facilities etc.). If you're planning go either side of the main season and trying to figure out what might still be open then don't expect to get much help from this guide. We were there around the last week of September and first 2 weeks of October (September being just in season and October being out of season).