Welcome Lively! I hope you found these forums useful and will write many more posts to come. As for Moon+ and series, I did some testing today. Personally, I always name my books by Author - Series # - Title, but not all people do; some prefer to edit that information in calibre, and they're perfectly within their rights to do so. I definitely agree that an ebook reader should recognize series information and/or offer means to edit it within the reader, so that's a minus for Moon+.
Here's what you see when you go to "My shelf" and long press on a book:
Add to my favorites, Edit book information, Remove ffrom my shelf, Delete book file, Add to home screen.
Choosing Edit book information, you get another window that enables you to change Book title, Book author, Description, and various Labels: Tags, and Favorite, where you can add a Category. As Teknikal noted too, there is indeed no way to edit series info unless you add it to the file name/title manually or in calibre. I thought there was, so I stand corrected.