The Warlock (Secrets of the Immortal Nicholas Flamel Series #5) by Michael Scott

Nicholas Flamel appeared in J.K. Rowling’s Harry Potter—but did you know he really lived? And his secrets aren't safe! Discover the truth in book five of Michael Scott’s New York Times bestselling series the Secrets of the Immortal Nicholas Flamel.

The Oaths: Many have made them.

The Betrayals: Almost as many will undo them.

The twins of prophecy have been divided—the end has begun.
  Josh Newman has chosen a side, and he will not stand with his sister, Sophie, or the Alchemyst, Nicholas Flamel. He will fight alongside Dee and the mysterious Virginia Dare.
  With San Francisco on the bring of ruin at the hands of Machiavelli, and Billy the Kid, Scatty, and Joan of Arc in another dimension called the Shadowrealm, the world stands at the edge of destruction. It is up to Sophie alone to find her twin before the battle begins pr all is lost—forever.
 
“The Secrets of the Immortal Nicholas Flamel has everything you loved about Harry Potter, including magic, mystery, and a constant battle of good versus evil.”—Bustle

Read the whole series!
The Alchemyst
The Magician
The Sorceress
The Necromancer
The Warlock
The Enchantress