If I Fix You hits the mark of a great YA perfectly. Abigail Johnson weaves an engaging tale full of characters as complex at their situations. You can't help but love Jill, she's honest and consistently true to herself - even in the midst of drama at home. She acts exactly how you would expect a 16-year-old in her situation to act - minus the whole being an amazing mechanic, I wish I had those sort of skills when I was her age! Actually, her whole being a mechanic and obsession with cars came across as very authentic, which is refreshing. 
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 The entire story has great pacing, and even though Sean was immediately identified as a guy-at-fault, I just knew there was more to the story. He was simply too incredibly likeable. I also really enjoyed reading the relationship between Jill and her best friend Claire, there is a really great conversation there where I think Abigail Johnson really captures the real nature of a lot of female friendships. Jill's father was easy to love, almost too easy - so I was glad when the author brings in some more backstory, by way of Jill's mother's attempt at manipulation, that really gives him more depth - which incidentally makes him even more endearing as a person. As for her mother, I want to say that it was easy to hate her. And it was. Especially with that opening chapter, I was fairly horrified and completely disgusted. But she also has a very interesting point of view, and I like that the author includes that - that there are multiple angles to examine a situation from, but that still doesn't absolve people from certain guilt. It would be easy to write a plain old evil character, it's more true to reality to write one that feels like flesh and bone - I think those are the characters who you feel like can cause the most harm. 
 I must admit I had some reservations when I found out about Daniel's age, the idea that a YA book might be romanticizing that sort of relationship worries me. The age of the youngest member of the YA target audience spectrum is an impressionable one. But I think the author actually writes that aspect of the story fairly well - no, I don't think 16-year old's should be encouraged to jump in a pool with their 21-year-old neighbor, and I don't think that in reality they should get involved in their adult neighbor's domestic abuse issues. Ideally Jill should have told her father. In reality, Jill could very likely have ended up in a bad situation - not all 21 year olds are nice guys who wouldn't take advantage of a "mature for your age" sixteen year old, and his mother could have been an even bigger basket case and could have hurt Jill. However, does this sort of thing [that 16 year old/21 year old thing] happen in real life? Of course it does, and while it reads really well in a YA novel and allows us and the character of Jill to take a closer glimpse into the horrors of domestic abuse, and the complexity of toxic parent-child relationships - which is definitely something I commend the author for tackling, as I don't think there is enough conversation surrounding the issue of abuse - I would still encourage young readers not to take Jill and Daniel's relationship as source of inspiration for how to behave when confronted with that sort of situation/opportunity. And please don't misinterpret this as criticism, it's just something that concerned me as I was reading the book. (hide spoiler)] 
 Overall, If I Fix You is definitely a great read. The star of the show is really the different relationships between the characters, the easy-to-love MC is icing on the cake.