Upon finding a Merchant that has this quest, talk to them and choose 'Cover To Cover'.
Cover To Cover
Ah! A fellow fighter I see! you look like you've seen a battle or two. I myself have known the taste of victory quite a few times. Though you should never be content with your current skill set. No, no. A good warrior always seeks to improve his game.
You know, you may be able to help me with something.
There's a book out there titled "A Pirate's Guide to Combat", that I've just been dying to read. Now I know, I know, I'm no pirate. But there's bound to be perspective in there that could prove useful, don't you think?
I would imagine some pirates higher up in the chain of command would carry such a book. If you come across one, would you mind bringing me a copy? In return I'd be willing to give you an axe given to me by a highly trained blacksmith. I think you would find it quite useful...