In August 2012 my brother died by suicide. In the dark days and weeks immediately after his death I read almost incessantly. I couldn't sleep because when I closed my eyes all I could see was his body (I had to go to the mortuary with my father to formally identify his body.) When I was awake I read so I could bear the raw grief ripping at my heart. I believe that it's thanks to books I survived those days, I'm not sure how I'd have coped without books giving me a respite from my at times overwhelming reality.The Humans wasn't published then but I wish it had been. It tells the story of an alien sent from the planet Vonnadoria to remove all evidence of the solving of the Riemann hypothesis (the key to prime numbers which guarantee a huge technological leap for mankind) by eminent Cambridge professor Andrew Martin. The Vonnadorians are horrified by this breakthrough as they see humans as a primitive, violent race not ready for the advancements the solving of the hypothesis will bring. An unnamed alien is therefore sent to Earth on a mission to ensure humankind remains unaware that this secret has been solved. He kills Martin then inhabits his body in order to infiltrate his life and erase all traces of his discovery, by removing all technological evidence and by killing anybody he may have told.The first part of the book has several comic moments, the alien arrives knowing nothing of human life and finds himself naked and without language on a motorway. Matt Haig has held a magnifying glass to humans here and through the eyes of the alien Andrew we see our often irrational absurdity.As the book progresses it becomes more poignant, Martin learns more about what it means to be human, thanks partly to a dog, peanut butter and Emily Dickinson. The 97 point list that features in the book is perhaps the book's shining moment, Matt's skillful blending of the emotional with the humorous means he avoids this list becoming saccharine and it is genuinely moving, my favourite point being "It's not the length of life that matters. It's the depth. But while burrowing, keep the sun above you."The Humans is a beautifully written insight into what it means to be a human and how pain, sorrow and fear are a necessary part of that. With my grief not being a linear process there are days when I am hit again with an almost unbearable sadness. I know that on those days I will turn once more to The Humans. I don't ever feel suicidal but there are times when I question what it means to live. When I read The Humans I am given an answer.