John Flanagan 
Brotherband 3 [EPUB ebook] 
The Hunters

It’s time for a showdown. Pirates vs Skandians. Bring it on, Herons! With Zavac and his ship, the Raven, well ahead of the Heron, Hal has a huge task ahead of him in finding the pirate — and retrieving the precious artefact Zavac stole from the Skandians. The Heron brotherband must undertake a long and dangerous river journey to hunt their prey. But even if they survive the journey, are they ready to confront Zavac in his lair? The third book in the New York Times bestselling Brotherband series, from the author of the international phenomenon, Ranger’s Apprentice.