I love introspective books, I love how Sally Rooney does it, I love how beautifully this book portrays grief from different points of view. I love how not just the thoughts themselves, but how the thoughts are structured indicates that the narrator has shifted. This is the first Sally Rooney books where some of the characters are actually likeable. 
Ivan, I’m so glad you escaped the edgy teenager to rabid misogynist incel pipeline. But Peter, you are my enemy number one. Stop calling her “the other” you ass, her name is Naomi. The fact that you use her as a rebound doesn’t define her, it defines YOU. 
(Although I will admit you did gain some points for acting like a nice brother by the end)