I was seriously considering rating A Monster Calls four stars, but today I saw the film...and I kind of liked it more than the book. 
 Personally, I enjoyed the visual effects and the general look of the film. The actors were equally amazing; none of them disappointed. It's basically a film I have nothing to complain about. The ending is even better than in the novel, with (view spoiler)[Conor discovering that his mother had called for the monster, as well (hide spoiler)]. It was noticeable that Patrick Ness had written the script, because many (beautiful) lines from the book could be found in the film. It also left out everything unnecessary, like Lily. While reading the book, I couldn't see the point of Lily (maybe just to show that certain friends never leave your side, no matter the past mistakes, right?) 
 The story was touching, combining fantasy and fairy tales with family drama in a way that is hard to describe. It's impossible not to like Conor, really. I was a little afraid I wouldn't be able to empathise with a kid whose mum has got cancer; I thought he'd be the "I-am-the-centre-of-attention-because-mummy-is-ill" kind of character. He never was. On the contrary, people tend to avoid him, to treat him as if he's made of glass, when all he wants is to be normal. I enjoyed "living in his head" while reading. 
 This was, also, my very first Patrick Ness book, and surely not my last one. I like his writing style: not exactly simplistic, yet easy to understand; not exactly full of metaphors, but emotional and sweet; not too much, not too little. Also, Siobhan Dowd deserves all the possible praise for her beautiful, imaginative mind. May she rest in peace.