Here Lies Arthur by Philip Reeve

The story of King Arthur as you've never heard it before. Arthur is the leader of a war-band. He is no wiser or kingly than any other man, but Myrddin, a storyteller, believes that Arthur will unite Britain again, and drive the Saxons from the land once and for all. Myrddin's stories, most of them completely fictional, spread, and Arthur's name is known.

Gwyna loses her home when Arthur's war-band destroys her village. Myrddin takes her in and uses her to help create stories with Arthur as the hero. Gwyna is the Lady of the Lake, a boy page, a lady's maid, anything that Myrddin asks her to become. Gwyna observes all that is happening in Arthur's quest to become King of Britain, and she isn't sure if it's for the best.

I listed this as fantasy, but it isn't fantasy, not really. It's the myth of Arthur with all the magic taken out of it. No wise, gentle King Arthur; instead we have the leader of a war band. No all-powerful wizard; just someone who can convince people with stories. No noble knights of the round table. Rival war-bands fight for land, betray each other and kill each other. Nothing magical, nothing noble.