Speaking Tiger The Lost Island (Gideon Crew) by Douglas Preston

Gideon Crew - brilliant scientist, master thief - is living on borrowed time. When he's handed an eyebrow-raising mission by his mysterious employer, Gideon has no reason to refuse. His task? To steal a page from the priceless Book of Kells, now on display in New York City, protected by unbreakable security. Accomplishing the impossible, Gideon steals the parchment - only to learn that hidden beneath the gorgeously illuminated image is a treasure map dating back to the time of the ancient Greeks, treasure that could, perhaps, save Gideon's life.