Told in the first person, this is about Artos the Bear, the great Romano-British captain trying to keep Sub-Roman Britain from being swamped by the Saxons. Some of the principal characters from the legendarium feature: Bedwyr is the Lancelot figure, Guenhumara is Guinevere, Ygerna is the vengeful half-sister and the creepily compelling Medraut is Artos's nemesis. No Merlin, no magic, but no less compelling and magical for that.
I love the Arthur myth stripped back to its bare essentials like this.
I couldn't put it down. Sutcliff writes amazing battle scenes (she did meticulous research with various historian friends), and the climactic scene when Artos' men crown him Caesar on White Horse Hill at Uffington (a beautiful, ancient place which I've been to myself) is very powerful:http://www.nationaltrust.org.uk/white-horse-hill/
But Artos knows that the sense of magic and destiny is illusory and that it's lonely 'above the snow-line', i.e. being Britain's saviour is a pretty isolating role. The ending, in which you see the seeds which would flower into the Avalon idea, is beautiful and very moving.
As ever, there are some great animal characters: hounds and horses feature a lot in Sutcliff's work - endearing, but never sentimentally done either.
She was both a great storyteller and a great stylist (qualities I prize in Tolkien, of course). Her writing style is both lyrical and grounded.
How disturbing is it? How often does it occur? And how much does it figure into the plot? I can't read it if it's prevalent, a big part of the story, and disturbing.)