My favorite books on writing are both by Lisa Cron (Wired for Story and Story Genius). I learned about the ever-important third-rail of stories, that inner journey. It's the journey we, as readers, relate to more than the external one. We actually root for the character to fulfill his/her inner need more than the outer need.
In Story Genius, Cron writes about finding the main characters mis-belief. Then she encourages you to dig deep into their past. Find their secrets. Find what they really want. Find what they believe is standing in their way.
I wish I had found Cron years ago. I truly believe, without any doubt, that her advice is what allowed me to finally revise my novel so that it resulted in a sale.
Having said that, I also love Bird by Bird (Lamott), Writing the Breakout Novel (Maass), and The Fire in Fiction (Maass).
Jody