This is me gesticulating wildly as I try to express to you how great this book is. This also means this review is going to be kind of meaningless because I'm still gasping for words.Let me share the first page: Today is Christmas Eve. Today is my birthday. Today I am fifteen. Today I buried my parents in the backyard.Neither of them were beloved.Awesome, right?That is Marnie speaking, and the story is split between her and her younger sister Nelly (who is 11ish, I think, at the start). Those first three or four sections almost undid me but I couldn't stop. They were dark, gross, grim, horrible, and deeply fascinating. Frightening, too: O’Donnell isn't painting a world of demon children or dystopic society; she's portraying contemporary Glasgow and the hard realities many children face. Marnie's parents are criminally negligent; they're drug addicts, alcoholics. Abusive in a variety of ways. Utterly unconcerned for their children, right up to their deaths. Marnie, well aware of what will happen to them if it gets out that their parents are dead, does what she can to care for her sister, Nelly, who is odd, speaks with an archaic kind of speech, and plays the violin like a prodigy.Eventually a third voice joins in, that of their elderly neighbor Lennie, observing from the sidelines -- a welcome adult voice for me, at least, since I kept biting my nails and sweating what might happen to Marnie and Nelly. (I fell in love with those girls from that first page. Marnie is rough and hard and damaged, and I just want to give her a hug and Nelly is so super odd and weird, and I just want to give her a hug. No matter their choices, I understood them and related to them and really really really cared for them.)Speaking of rough, hard, and damaged, this book might need a trigger warning, especially for those who are uncomfortable with implied sexual abuse, adults having sex with underage girls, and drug use. (Or, if you're the parent of a young teen, this might give you the jibblies.) Still, I never felt O’Donnell was being gratuitous or shocking for the sake of the shock -- Marnie's world is all-too real for many children.I will admit, there was one moment in my marathon reading when I thought 'I just can't take any more misery' but O’Donnell holds the story together and pushes the boundary of misery without breaking it, and the end wrapped up neatly and satisfactorily. I can't stop talking about this book and woe be anyone who makes eye-contact with me over the next few days, because I'll be babbling about it non-stop. Give this one a read as I think it is worth the buzz!