This book was in a word - brutal. I saw it recommend in a horror group under a list of most disturbing books people have ever read. I can confirm that, yes, it's gory, graphic, and at times difficult to read. I really enjoyed how the author explored luck (this is expanded further in the sequels). You grow to care about these characters before the true horror begins, and that makes it all the more gut-wrenching and heart pouncing when it really gets into it. Some scenes don't hold back on the details, while other scenes leave the worst to our imagination- not sure what's worse!
I saw a ton of reviews and hype about this novel but I'd encourage you to check out the next two books. These are set many years in the future and are less gory but fantastic reads and explore some very curious and fun ideas.