Whether I’m sitting down to write a book or a screenplay, my process is similar. For a long time I think about the characters and their world and let that sort of “percolate” in my mind. Then once the characters feel “real” enough to me, I soft test the concept with friends and colleagues of all different ages, nationalities and backgrounds. Sort of a…”would you be interested in a story about….X,Y, Z” and if I consistently get a “yes, that sounds intriguing” then the next step for me is writing a very detailed outline. That can be anywhere from ten to thirty pages, including some dialogue as reference points. Once that is done, I break the treatment into story arcs, character arcs and chapters. That has always been my process. I feel it really helps to have a sort of road map, before you dive in deep to the book.