I'm not sure how I feel about these digital shorts overall - not just Veronica Roth's versions but the short stories that are multiplying in between releases of the major books in these Y.A. sci-fi trilogies. The authors are kind of between a rock and a hard place because they have to say something new without giving away the plot for those who haven't yet read the main books. In The Transfer, I felt that there just wasn't enough "new" going on to perhaps justify a whole story. But I liked Free Four. Of course, authors can go the other way and potentially give too much away about their characters. For example, even though I largely enjoyed Tahereh Mafi's Destroy Me - the short story in between Shatter Me and Unravel Me - I felt it gave away too much of Warner's character and perhaps took away some of the surprises I would have otherwise enjoyed in the second book. Veronica Rossi tried with Liv and Ror to give us some insight into Ror's character, again by telling us things we already knew from her first book - Under the Never Sky - but she did it in a really sweet and engaging way.
One of my favorite "shorts" has been Brodi Ashton's Neverfall which gives the reader some deeper insights into Cole from Everneath and Everbound. Neverfall worked for me because it told a new story that wasn't necessarily closely related to the action from the main books in the trilogy - not a retelling of events we saw in the main books, nor necessary information for us to know to understand the plots of the main books. At the same time, it did give new insights into a major character whose actions are a little ambiguous in the main books. So I'm kind of agnostic about whether these digital shorts overall are a good idea or not. They are a great way to engage readers and keep them interested between major books in a series, and they certainly can generate ideas for the writer. But they are a tall order for writers who are likely in the middle of drafting the next book in the series and I wonder how those writers feel about being taken from their main task to also produce shorts. I know that looking at a character/situation from another perspective can help the overall writing process on the main books, but when that exercise also has to be sold commercially, I suspect it puts a lot of pressure on the writer.