One challenge facing most writers is how to detrmine if a short story, Poem, or book is done. You hear the same from artists and scultors as well. Show your work to another person. If you have a Beta reader solicit their thoughts, Remember, if one oersoin says you need more material to make it a good mbook, it's only the opinion of one person, Get the opinion of someone else before you decide whther or not it's time tio go on to the next project. If you do, don't look back.