Literary Phenomenon

Here's something I've pondered recently. I was reading the book "The Kite Runner" by Khaled Hosseini a few weeks back. I was about halfway through the book and was enjoying it immensely. However, up until that point, I was under the misconception that the book was nonfiction. I believed the characters were real people and felt for them as the conflicts of the story arose. At some point, I noticed that the main character's name was different from the author's and felt the need to do some research. That's when I found out it was fiction. The rest of the book was less satisfying to me and in certain places predictable. In others the author asked me to suspend too much of my disbelief. Yet, a few days before, he wasn't asking and I was believing. The only thing keeping me from blaming my perceptions entirely is that the part of the book where I felt compelled to check constituted a major change in the flow of the story. So, I don't know if the writing led me to question or my question led me to doubt the writing. I think it was still a good book and I would be interested in the thoughts of others reading it knowing it was fiction the whole time. Anyone else ever have an experience like this?