There are always two novels: the written one and the one in the writer's head. Unfortunately, the reader only ever gets to see the written one.
Knowing this truth intellectually doesn't always help. When you read your work back to yourself your mind plays a trick on you, filling in the blanks so that the picture you have created seems clear and vivid; even when it's full of holes. That's why it's important to get someone else's opinion on your work. Preferably someone who isn't emotionally involved with you. Or, if they are emotionally involved, someone who you can rely upon to be absolutely honest.
What you want that someone to do is to bridge the gap between your vision and the words you have used to describe that vision. Because it is the words that matters. Without them the vision has no existence outside your imagination.
The fact that you, the writer, know all about the characters and the setting is worth nothing if it is not there in those words. No matter how much you feel they should, the reader will not be able to intuit it. They will just think, 'Who the hell are all these people and where is this story supposed to be taking place?'
Then they will put the manuscript down and do something more interesting.