One of the perks of self-publishing is the option to revise either or both of the cover and interior and republish a book whenever you like. You can fix typos, improve a character arc, patch up plot holes, and even add illustrations. You can make a previously standalone book part of a new series by adding branding to the cover. You can even change the title. Just remember that you must use a new ISBN for any major changes. I first published Madison Lane and the Wand of Rasputin in 2014, and have been meaning to make some changes for years. Finally, with a book fair looming (which I unfortunately had to pull out of, after all that) I busied myself with updating the cover design and adding my Grounded series branding. I also revised the story to add some explanation to a few cryptic references that were originally only going play out in later books, and I fixed a characterisation inconsistency that was a hangover from the very first draft of what was originally a very different book.