The moral is that Matsuri is her ever-changing book.
And by the end of the book, she'll end up loving her.
And they lived happily ever after.
I do think that by the end they'll probably be together, if not outright said, at least kind of like Ebisu and Hotei, heavily implied.
Plus how is it not yuri? I haven't read it in a while but I recall that the MC is in love with/has a crush on the librarian, the MC's sister as well has a crush on her.