Sophie and Josh Newman are twins who have pretty average lives until, the bookstore Josh works in is attacked by a magician and dead-looking creatures that he controls. The man is seeking old book, and he wrenches it from Josh's hands, grabs Perry, and flees before realizing that two of the book's pages ripped out in the struggle and remained with Josh.
Josh, Sophie (who witnessed the attack), and Nick Fleming are forced to run for their lives before the magician discovers the missing pages and returns for them. Nick reveals that he's actually Nicholas Flamel, an alchemyst who discovered the secret of immortality in the book that was just stolen, and that he and Perry (Perenelle) are both around 700 years old.
Josh and Sophie are sucked into a dangerous, potentially deadly adventure to save themselves and Perry and recover the book. They encounter magic, alternate realms, and ancient gods and goddesses that were supposedly mythical but are actually members of the Elder Race, powerful beings that once ruled the world--some of whom are intent on destroying the human race to reclaim the Earth for themselves.
I'm incapable of a short plot summary. Anyway, I very much enjoyed this book. I have a preference for books with romantic plots/sub-plots, and this (as with many children's books) didn't have one and still managed to keep me interested. I loved all the mythical elements, and I was sucked right into the adventure.