Reality and the novel should go hand in hand. This doesn't mean you have to know everything but you should have researched what you're talking about. But I'm writing fantasy and there's nothing known about something that is strictly imaginative. You're wrong. To create a world you need to have facts to bring the world to sound like a real world. That you need to do even if you;re writing a contemporary or a historical. One rule is to read and research. Then you will have facts to sprinkle in and give your stories a sense of reality. I often write medical kinds of books. Now there's a lot that happened since I last practiced in that career. So now I research. Watch when I'm somewhere medicine is practiced and ask questions. That's how you give the world you're writing about the illusion of reality.
Remember the emotional reactions of your characters. That can help give the illusion of reality no matter what the world you're creating. How does your character react when the phone vibrates in his pocket or some known ring occurs as she's settling down to sleep. Use the emotions of your chanacters to show the facts of the world you're creating.
Just what is unity. I've read some novels that I thought were scattered. I never could put my finger on why. Were there too many characters, too many changes of scenery, too many problems to be solved. In some cases this was true. Others never did. I often ask myself why did the author write this book. The answer is that I don't know and probably they didn't either.