This Forsaken Earth by Paul Kearney
Nothing moved in all that tangled mass of wreckage and shredded cordage and shattered spars. All along the decks, flesh, wood and iron had been beaten into one unholy, pulped mess from which trickled streams of blood that brightened the brown stains venting from the scuppers. The enemy vessel was a dead thing, which even the wind could no longer stir to life. The Revenants stared around themselves in heavy wonder, as if uncertain as to who could have brought such a thing to pass. A silence fell, broken only by the weary creak and groan of seaborne wood, the death rattle of a tall fighting ship. There was a moment almost of reverence. 'This' Rol said, 'is victory.' But no-one can outrun their past, as Rol Cortishane discovers when his old acquaintance in murder, Canker, King of Thieves, turns up unannounced to make Rol an offer that cannot be refused. To safeguard the hidden pirate city that has become his home, Rol must leave behind his beloved ship, Revenant, and take to the mountains of Bionar, where his sister, Rowen, is fighting to take possession of the mightiest kingdom in all the world. Amid siege, pitched battle and betrayal, Rol will discover that his world is not the place he thought it was, and he must relearn his assassin's skills in order to survive...