The strongest aspect of If I Stay were the secondary characters, especially Mia's boyfriend, Adam, and her best friend, Kim. Both were likable and felt very real. I could identify with their pain and fears of potentially losing a loved one, and I loved their personality quirks. Even the minor characters such as Mia's parents' friends and Kim's mother were well written. Although we didn't learn as much about them as some of the other characters, the parts we did learn about felt real.
What didn't work for me in this novel was Mia, and to a smaller extent her immediate family. I did not relate to Mia at all and I found her mostly unlikable. Part of this was because her character was inconsistently written. There was a disconnect between what we're told about Mia and what we're actually shown. For example, Mia constantly brags about how humble she is. Someone who is truly humble doesn't brag about it. Additionally, I didn't think her actions showed her to be a modest or humble person.
Mia was also a bit too perfect, and I found that her idol status among those who loved her just didn't ring true. I found it odd that Mia's parents and brother recently died, yet none of the family reacts to it. It is all about Mia. Although the focus should have been on her since they were at the hospital visiting her, I felt that there should have been more acknowledgement of the three members of the family who didn't make it. Also, in the flashbacks Mia seems to be at the center of everything in a way that screamed Mary Sue to me.
I also felt that Mia's immediate family was a little underdeveloped. While her mother comes across as sort of a bitch (though never to Mia), her father is flawless. Her younger brother seems to be a character whose only purpose is to be cute and worship Mia. They did not come across as well rounded characters. Additionally, like so many other novels, both adult and YA, the younger brother did not sound like his age. His dialogue was much too mature as were a lot of his thoughts.
Overall, I enjoyed the novel, but not being able to relate to Mia kept this from being a truly great read for me. I enjoyed the sequel, Where She Went, a lot more than this one.