In New York City, bookseller Cassie Andrews is living an unassuming life when she is given a gift by a favourite customer. It's a book - an unusual book, full of strange writing and mysterious drawings. And at the very front there is a handwritten message to Cassie, telling her that this is the Book of Doors, and that any door is every door.

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What Cassie is about to discover is that the Book of Doors is a special book that bestows an extraordinary powers on whoever possesses it, and soon she and her best friend Izzy are exploring all that the Book of Doors can do, swept away from their quiet lives by the possibilities of travelling to anywhere they want.

But the Book of Doors is not the only magical book in the world. There are other books that can do wondrous and dreadful things when wielded by dangerous and ruthless individuals - individuals who crave what Cassie now possesses.

Suddenly Cassie and Izzy are confronted by violence and danger, and the only person who can help them is, it seems, Drummond Fox. He is a man fleeing his own demons - a man with his own secret library of magical books that he has hidden away in the shadows for safekeeping. Because there is a nameless evil out there that is hunting them all . . .

Because some doors should never be opened.