This was the 1978 Hugo winning book.
The curtain opens on a young healer named Snake, a young woman who uses actual altered snakes to heal people. She is helping a young boy with a tumor, by spurring one of her snakes to attack it, poison the cancerous bit and save his life. While this happens the boy's tribe kills one of her other medicinal snakes out of fear. This is terrible news for Snake since her helpers are rare and difficult to breed.
The curtain opens wider and we see that this is a post nuclear war world, probably Earth. There are still small tribes and towns and levels of technology vary greatly. Snake is afraid that she won't be allowed back with the other healers after losing her snake. She sets off on a quest of sorts, picking up new obligations and directions as she goes.
This won both the Hugo and the Nebula (British sci-fi award) so it must have been well thought of. From this vantage point it's hard to see why. Not that it's a bad book by any means, it just isn't all that good. The world building is interesting but not spectacular. The ideas don't really 'wow' and the writing isn't all that special. McCafferey's 'White Dragon' was nominated for the same award and it's a much better book in many ways.