The Bloodline Cipher by Stephen Cole
Jonah and the rest of the elite team of teenage thieves have been sent on a mission by Coldhardt to retrieve an ancient grimoire. He believes it to be a magical book of the law of the dead. Something like that could fetch a very good price in the right market. But when they go in to get it, the discover another team of thieves has beaten them to it. Even more disturbingly, this team is better trained, and better informed. It seems Coldhardt's old mentor, a man he thought was dead, is not only very alive, but has a highly efficient rival organisation, and a devilish plan to wipe out Coldhardt. Only the best will make it. In a thrilling adventure with brilliant plotting and fiendish twists, join Jonah faces his toughest challenge yet - but will it be his last?