Maybe it's my fault for not skimming this properly when I picked it up in the National Museum. I got the impression it'd be more about the meaning of these patterns rather than the mathematics. But it certainly gives you an appreciation for the intelligence and familiarity with geometry these artists had.
It would be unfair to rate it poorly on something I thought the book was going to be, rather than what it is. But I found that, when this does attempt to provide some information beyond the geometries of these patterns, it makes odd, sweeping claims that are backed up with little clarification, let alone evidence. One such instance claims that these patterns brought Celts closer to "The Goddess." Which Goddess? Your guess is as good as mine!
Hope this would give me some neat symbolism to work with for my own writing, alas.