I wish I had known about that book. I just followed the main route and it seems to me, now, to be a tad dumbed down. The fact that the Devil's Staircase is presented as a major obstacle that you have to overcome is a bit of a joke. The GGW is even more of a walk in the park. These routes are really good beginners routes to get you into multi day trips in a low risk low reward kind of way, IMO, but there is so much more reward if you do your own thing. "Not the West Highland Way" may well be a way of still having your hand held whilst experiencing a bit wilder country.