Hearne, Kevin. Iron druid chronicles.

"This hilarious and action-packed urban fantasy series is set in a modern world in which all the gods of every pantheon are alive and well, as in American Gods; its hero is a smart-mouthed, buttkicking magician, like Jim Butcher's Harry Dresden. But it's told in a smart, witty, unforgettable voice that's all Kevin Hearne--a rising star in the fantasy world. This addictive and wildly imaginative series stars hero Atticus O'Sullivan: a handsome, tattooed Irishman who looks like a young rock star, but is in actuality a 2,000-year-old Druid with extraordinary magic powers. In Shattered, Atticus and his apprentice Granuaile travel to India to battle an ancient plague-summoning demon...and meet an important person from Atticus's past!"--