The Book of Doors by Gareth Brown

Bookseller Cassie Andrews feels something is missing from her life. Then a favourite customer gives her a curious old book. In the front is a handwritten message: This is the Book of Doors. Hold it in your hand, and any door is every door. As Cassie discovers, this is a very special book: a magic book that bestows extraordinary abilities on whoever possesses it. And there are other magical books that can also do wondrous - or dreadful and terrifying - things. But where there is magic there is power - and there are those who will stop at nothing to possess it. Suddenly confronted by shocking violence and danger, Cassie turns to Drummon Fox for help. He is a man fleeing his own demons, including someone - nameless and evil - who is hunting them all... Because this book is worth killing for...