PeterH,
I had a flick through it in a bookshop in Ambleside. Judging from the photos, I wasn't too sure about the interpretation of the various features, e.g. boulders, as waymarks. There are any number, in my opinion, in the area that could easily be made to fit the theory. Having said that, I haven't read it, it was just my first impression.
Cheers,
TE.