For me, I couldn't help comparing this to 'A Walk to Remember' by Nicolas Sparks or to 'A Fault in our Stars' by John Green. The characters are similar to that of A Walk to Remember where you have quiet shy girl who is sick and the bad boy who wants to be with her. Then you also have the similar family dynamics as A Fault in Our Stars, where the family is very close and she doesn't want them to be hurt etc. 
 This though didn't work for me. I do admit that I did feel emotional reading towards the end, and depressing as it may be, the end was my favourite part. I didn't beloved Damien's character so much and I don't understand how suddenly he nearly overdoses on heroin. It seemed quite random and didn't fit into the story. Yes, he drank a lot but he suddenly does heroin but kicks it straight away. 
 I think if you have read anything similar then it would be a tear jerker. It annoyed me when she gave up and she didn't take the chance on the trial. But not my place to judge. She even doubted herself so many times. 
 And Damien, I really couldn't stand him sometimes. He says he loves Kate but he will sleep with someone literally after she was buried. Instead of changing for the better, not just for him but for her. Then there were times when he was adoring to her and was literally with her till the end. 
 I am aware of a sequel told from Damien's point of view 4 years later. I may give it ago some other time. 
 Warning if you don't want to experience anything about cancer or dying then maybe skip it for now.