The clouds in the blue were scalloped and articulated like driftwood, and crawled around in themselves like otters at play. He could see everything at once. His spirit kept tugging at the top of his head, lifting him so that he had to concentrate to keep his balance. The problem made him laugh. The world was so great, so beautiful. Something like a lion: it would kill you if it could, but in the meantime it was so very, very beautiful. [loc. 806]
The eponymous shaman is Loon, who at the beginning of this novel is sent out to wander for two weeks in the freezing wilderness of late winter in Ice Age France. It's a fortnight of minute-to-minute survival, and at times the whole book seems to be first and foremost a wilderness-survival narrative. It's quite slow-paced, and a great deal of it is concerned with the daily grind of Paleolithic life.
Loon, though, embarks on journeys which have the weight of proto-myth. When his wife is abducted by her former tribe, Loon goes after her: he finds a community which has learnt to domesticate wolves, and thus -- the parallel is explicitly drawn -- to enslave humans. (Because this community has more food to spare, they also have more rules about how that food is distributed: an interesting observation.) Later in the novel, one of the most basic human taboos is broken so that others may survive. Loon and his companions, without benefit of maps or compasses or GPS, are lost wanderers, yet they finally find their way home.
Robinson's known as a science fiction author, and there is a science-fictional feel to Shaman, perhaps because the world it describes is so different to any reader's experience. Robinson drew on his own experiences of hiking in winter, which gives descriptions an immediacy: but he had warm clothes, enough to eat, and no doubt a plethora of artefacts to make his journey easier than Loon's.
There's an element of the fantastical in the narrative voice: it's the 'third wind', an inner last-ditch strength which might be something mystical or something primally biological, a survival instinct buried deep in Loon's unconscious mind. Another fantastical element is the occasional switch of viewpoint character: to a cat (delightful!), a Neanderthal, a wolverine.
One minor niggle: Robinson has said that he's used Basque as an inspiration for the novel, "...that the Basque people have a larger portion of Neanderthal DNA than anyone else in the world, and that their language is the oldest in Europe and dates to the time period (and to the setting actually) of [Shaman]." (source). Fair enough -- it's not as though he's attempting to transcribe paleolithic speech -- and the occasional word is fine. But there are times when it obfuscates meaning: Loon describes the first in a series of caves as "In Mother Earth’s body, it was not the sabelean but the baginaren": I had to look up those words, though perhaps I should have guessed that they were gynaecological terms.
The society Robinson describes is, despite the novel's title, surprisingly secular. There is mysticism, in its primal form of awe at the natural world; the spirits of the dead, both human and otherwise, are presences which must be respected; but there are no gods. Loon's duties as shaman are more prosaic: remembering oral histories, painting animals on cave walls, communicating with the Old Ones, respecting the dead.
... Thinking about it, it feels as though this is pre-god territory: that the invention of gods, initially as personalised natural forces, implies a relationship in which humans have anything at all to offer such gods. All Loon's people can do is survive.
Throughout Shaman, the question of what it means to be human is examined. It's there in the interactions between Neanderthals ('Old Ones') and Loon's people ('Fast Ones'); it's there in the enslavement of humans by other humans; it's certainly there in Loon's art, and in the descriptions of the great summer gatherings, and in Loon's sheer joy at the beauty of the world.
As a reader with fond memories of Jean Auel's Clan of the Cave Bear and sequels, I can't help comparing Shaman. Both are well-researched, though Robinson has more recent sources available to him. Auel's novels focus on Ayla, who's pretty much a Chosen One, special and unique and better than the Neanderthals among whom she spends her childhood. She's an innovator. For the first couple of novels she is more or less alone.
Robinson's Loon is a part of his tribe: he doesn't care for being alone, doesn't invent anything (though he might develop new artistic techniques) and there is nothing unusual about him. His stream of thought is more comparable to a contemporary teenager's than is Ayla's. His actions are mundane, but his emotional and spiritual life is more richly described: I much prefer Robinson's style to Auel's.