If you’ve written a series, consider packaging them as a boxed set when it’s complete. This is a chance to revitalize it with all the push of a new release and it also eliminates the cliffhanger issue. While pricing may be a challenge since you probably won’t have much success by making it the same price as if they’d bought each one separately, they do tend to be popular, especially for those who are familiar with the story or your work.
Including bonus material is another way to lure in readers. As far as I know, none of the POD paperback suppliers make it easy to do this as an Indie writer as far as packaging. However, you can do so yourself for signing parties and book fairs.