Alan Dean Foster 
Spellsinger [EPUB ebook] 

It was where beasts walked and talked as men, armed with swords and daggers. And it was where Clothahump, turtle and wizard, stretched his powers of sorcery to their limit, reaching out to another universe, seeking help to combat the force of evil emanating from the dreaded Greendowns. And so Jonathan Meriweather found himself plucked from his peaceful university life and catapulted into a strange new world to become part of a very strange fellowship. Soldier and crusader, fighting with sword and song, he is the Spellsinger.