I had missed the announcement of this final epilogue to the Divergent series completely, but don't worry, you won't miss a thing.
It's five years since the events in Allegiant (which was a ridiculous book and I'm still being kind), and I didn't have a strong desire to go back, but the completist in me wanted to have read the entire series, so here I was, reading We Can Be Mended.
And they get mended over the course of this 27 page story. I've seen a lot of people hate this story with a passion, but I'm more indifferent. I only got the slightest of information on how the world changed and what is going on now. Instead there's the rather forced coming together of two of the surviving characters from the book.
I would only recommend it for big fans of the series, and even then prepare to dislike it.