Pace is crucial. Fine writing isn't enough. Writing students can be great at producing a single page of well-crafted prose; what they sometimes lack is the ability to take the reader on a journey, with all the changes of terrain, speed and mood that a long journey involves. Again, I find that looking at films can help. Most novels will want to move close, linger, move back, move on, in pretty cinematic ways.
Rose TremainIn the planning stage of a book, don't plan the ending. It has to be earned by all that will go before it.
Rose TremainWhen an idea comes, spend silent time with it. Remember Keats's idea of Negative Capability and Kipling's advice to "drift, wait and obey". Along with your gathering of hard data, allow yourself also to dream your idea into being.
Rose Tremain