How different writing a book is from reading one. When you read a book, no matter how much you are engrossed between the covers, when you get to the last page, you most likely put it away and pick up a new book to read.
However, the writer is stuck in that same book for days and weeks and months and sometimes years. We live inside the book differently than our readers, even our most obsessive readers. We walk the land, shadowing our heroes. We are the first to taste the poisoned draught. We feel the knife's blade go in. We weep, we laugh, we feel the north wind like a slap against the face. We take out the poison and put in a sleeping potion. We change the knife to a sword. The north wind circles around to the east. We feel it again.
So when you are writing, better be certain that particular novel is a place you want to be. You are going to take up residence there for quite some time.