It was a really strange and cobbled-together-feeling anthology that, with a few exceptions, most of its stories have Rio being the butt of jokes and don't seem to understand what made him interesting and beloved by fans in the first place, and none of them were funny in the slightest, they're just needlessly mean-spirited and not fun to read. It's as if the author approved these Rio-centric stories haphazardly with no regard to their tone or what they have to say about the character.
I wanted to like this anthology because I was so attached to Rio more than any other character in KiraKira, but it was very disappointing, unfortunately.