I started to read this book a while ago and did not finish it. I would like to read it again.
A girl was walking down the stairs while reading a book when she fell and landed on top of the book and she was sucked in. She was transported into a medieval world where there is a war. She realizes she was in her book. She join with the characters in the book to fight the war. It's in English, I read it somewhere in 2009-2011, and if I'm not mistaken the book had a green cover with a picture of a castle.