One fun way to create demand and help people get into what you are working on is to have them feel like they are a part of the process. Of course people can always leave reviews which is one way to feel like they are participating but another way is to add a book in progress section either on social media or your personal website.
If on a website you can have an actual link or tab that would take your readers and fans to a section that you can update every day or week showing how you are doing on whatever our current project or projects are. Whether you choose to do a graph to show how close you are getting to completion or update your word count, think Nanowrimo, there are a number of ways you can show how your progress is going.
Social media may be slightly more difficult because there is no current app to add that I have found for Facebook or anywhere else that can show progress of this type. For social media having a set day of the week or time of day to update your followers would be the easiest way to keep everyone up to date. I am working on implementing the social media side of this since I do not currently have a website though I am hoping by the end of the year to have that part as well.
It is possible of course to use this idea to update on multiple projects and even after the writing process if you are submitting or self publishing you can continue to post updates. Adding excerpts from the stories at different milestones can also help to keep the readers engaged and then give you a chance to interact with your readers by getting feedback or taking questions and having the chance to talk with them about what you are working on.