I read this out of order... it's supposed to be read after Losing Hope, Holder's POV of the Hopeless Series. That being said I think it really wasn't a big deal, it says that it can read as a stand-alone.
This is a very cute novella about Sky's friend Six and Holder's friend, Daniel. Both are totally loveable and it's also totally worth the read. I believe it was free too, still is, actually. If you've never read any of Colleen Hoover's books, this could be a good place to start.
Now, hopefully, someday I can actually get around to reading Losing Hope.