The Book That Wouldn't Burn by Mark Lawrence

A boy has lived his whole life trapped within a vast library, older than empires and larger than cities.

A girl has spent hers in a tiny settlement out on the Dust where nightmares stalk and no one goes.

The world has never even noticed them. That's about to change.

Their stories spiral around each other, across worlds and time. This is a tale of truth and lies and hearts, and the blurring of one into another. A journey on which knowledge erodes certainty, and on which, though the pen may be mightier than the sword, blood will be spilled and cities burned.