The Magician by Michael Scott (The Secrets of the Immortal Nicholas Flamel: Book 2)

Ashes to ashes... California: the book of Abraham the Mage holds the secret of eternal life - a secret more dangerous than any one man should possess. Dr. John Dee is two pages away from the knowledge that would bring the Dark Elders into ultimate power - and could mean the destruction of the world as we know it. Two people stand in his way: Josh and Sophie Newman. In Paris time is running out for Nicholas Flamel and his wife Perenelle. Every day they spend without the book, they age one year: their magic becomes weaker and their bodies more frail. Niccolo Machiavelli, immortal author and celebrated art collector, works for Dee and is in hot pursuit of them - Flamel knows there's no time to lose and Sophie must learn about Fire Magic... Josh and Sophie are the world's only hope. If they don't turn on each other first.