As many reviewers have mentioned, you really must read the paper copy of this book so that you don't miss out on the beautiful, dark, and sometimes haunting illustrations that accompany this story. They were done by the incredibly talented Jim Kay, and some samples can be found on his website.
Coner is a character that everyone can relate to, whether they've been in the same situation as him or not. He feels invisible, misunderstood, angry, and confused. His complete belief and hope in his mother's recovery was both inspiring and heartbreaking, and there were many times where I just wanted to reach into the book and hug him.
I just loved the monster. To me, he was the embodiment of truth: paradoxical in all ways, and not always the easiest to face. As the yew tree, the monster was both capable of healing (through the treatment) and harming (through the poisonous berries) an individual. It was able to show Coner difficult and confusing truths about the world itself: that good and evil aren't as clear-cut as we'd like to imagine; that sometimes being seen is worse than being invisible; that stories are incredibly important; that sometimes it's easier to lie to ourselves than to face the truth. Most importantly, though, the monster showed Coner the truth that he had been hiding from himself, and how his thoughts are just that: thoughts.
A Monster Calls is something that everyone should read, whether they've experienced loss or not. We cannot all have a monster calling our name to teach us important truths, which is why this story is so important: it's beautiful, powerful, heart-wrenching, and healing. It reminds us to treasure every moment, to love fiercely, and to forgive both ourselves and those around us. It's a story that touched me personally, and will resonate with me for quite some time.