This book was cute! The blurb is somewhat misleading, to be honest. When We Collided is presented in two point of views - Vivi's and Jonah's. To me, Vivi felt like the main character between the two, maybe because she was so much more outspoken than Jonah. 
 These two characters are vastly different. Vivi has a bipolar disorder, but hides it under an eccentric personality. She brings Jonah and his 5 siblings back to life, in the sense that she teaches them the meaning of having fun again. Jonah is not the oldest child in the family, but he acts like the parent since his dad died and his mom is suffering for a sort of depression. He is more quiet and reserved, but loves cooking. 
 Warning, it was very insta-lovey between them. I mean within the first 5 chapters or so, they were together. But I guess the book had to be that way, because it was about them trying to figure each other out, especially about Jonah trying to understand and deal with Vivi. Them 'colliding' was beneficial to each other in the long run, but at first she did seem to really just push herself onto him, and he just seemed to accept it. Not really shipping them... 
 What I did enjoy is how the story was told. I haven't read many books about people with mental disorders - the main one I can think of right now is The Shock of the Fall, which I highly enjoyed. This one was almost set up in the same way - the main character never says whats wrong until the last few chapters. This book did it well, but had less of an impact. A few times, Vivi left me feeling confused and upset at her for treating her friends in family the way she did, until I understood what was going on. 
 However, I did enjoy Vivi's brightness. She painted life and ideas so vividly (pun not intended), you couldn't help but want to just go full carpe diem all day! Also, her relationship with Jonah's siblings was amazing, I loved those parts so much! :D 
 Overall I'm giving this a 3.5/5 stars. I enjoyed reading it, it was cute, but it didn't completely blow my mind, or made me very emotional.