"Reading a book is like rewriting it for yourself. You bring to a novel anything you read, all your experience of the world. You bring your history and you read it in your own terms." -Angela Carter
Though we may rarely think of this, it is very true. No matter what you write, how many details you spell out, or how clear your own vision is, your writing is never concrete. While it means one thing to you, it can have an entirely different meaning to your writer. If you give over your manuscript to your best friends, they might come back with five different interpretations of what the story meant to them, that are different from your own intention. This is normal, and great!
While it might be scary to think that your work will take on a life of your own, it's more like raising a child than creating a zombie. You shape it, structure it, help it grow and give it all the right resources, then let it free into the world. You can't control what it does from there, but you hope and pray that it will accomplish great things and change a few lives for the better along the way. You can't control its personality, or direction, or motivation, all you can do is watch. You have formed this wonderful creation and now you must let it live its own life.
All authors hope that their novel will sell across borders and last through generations. Take, for example, the diary of Anne Frank (not meant to be a worldwide novel, but it has become that). At the time she wrote it, it had a certain meaning because of the context it was written and the state of the world at the time. It was raw, real, and current. Now, it is a window into history and, while the writing is the same, the meaning within the pages has changed. And it means an entirely different thing in modern-day Germany than it does in South Africa, the rural United States, or the big cities of Japan. Anne Frank could have never predicted the impact her writing would have or the various interpretations her diary would inspire, but it has done that, all the same.