“They” always say that you should see the movie before you read the book because the movie will always be a let down compared to the image you created in your own head. When we read, the words on the page shape the vision in our heads. When we go see the movie, there is no way it can match the vision we created. If we see the movie first, we already have an idea of what characters, scenes, etc. look like for when we read.
When we read the Bible, our minds do the same thing. We create these characters in our heads. These people really existed though, and we can’t create the exact image in our mind. We often do this with Jesus. We shape Him into the character we want Him to be based on what we read.
The problem with creating a character for Jesus is that the character in our mind ISN’T Jesus. We think all He wants is for us to be happy all of the time. Or we think He didn’t really teach THAT (whatever THAT is that you disagree with). When we create our own “Jesus,” we limit Him. The real Jesus is far more awesome than our flawed image.