Here are remarks on Red Shift that I posted here a few years ago. They give away some plot details.
I read Alan Garner's Red Shift for the second time about a week ago (on the Saturday), and then for a third time Friday-Sunday just now (this is Monday). It seems to me as if Garner got a bit carried away with the experiment of writing a novel as much as possible through terse dialogue. The deliberate anachronism of having the remnants of the Ninth Spanish Legion speak like US soldiers in Vietnam doesn't hold up. Various other details may be criticized, but, more basically, I am in doubts about how genuinely the three time-lines relate to one another and whether there is indeed significant real value added, by having the axe head in each of them, etc. I'm particularly doubtful about the 17th-century element, which feels to me like it might have been included largely to make up the full weight of a novel that's somehow about the passage of time in the same geographic area. The man with epilepsy seems "needed" for the novel a little too obviously, so that we can have a severely-stressed male character in each time-line (the berserker soldier in the Roman-period one, and the unhappy lower-class teenager in the modern one). I've liked the cyclical time thing in Owl Service, the preceding novel, more, which ends redemptively, whereas this one ends with the teenage boy probably killing himself &c.