Hild by Nicola Griffith

You are a prophet and seer with the brightest mind in an age. Your blood is that of the man who should have been king. That's what the king and his lords see. And they will kill you, one day. Britain in the seventh century - and the world is changing. Small kingdoms are merging, frequently and violently. Edwin, King of Northumbria, plots his rise to overking of all the Angles. Ruthless and unforgiving, he is prepared to use every tool at his disposal: blood, bribery, belief. Into this brutal, vibrant court steps Hild - Edwin's youngest niece. With her glittering mind and powerful curiosity, Hild has a unique way of reading the world.