Patrick Ness on the changes to bring A Monster Calls to the screen

A Monster Calls is in cinemas now, and it's a visually and emotionally spectacular film from J.A. Bayona, the director of The Impossible.

The film is adapted from the book by Patrick Ness, and is all about a young boy called Conor who is struggling to deal with his mother's illness. At night, he's visited by a monsterous creature, who is voiced by Liam Neeson in the movie version.

Ness got the chance to adapt his own book for the screen but as we all know there are a lot of differences between novels and films. And in the case of A Monster Calls a number of changes were made, including dropping a major character and inventing some impressive new visuals.