Memento is a novella set in The Illuminae Files universe. It doesn't feature any of the human characters from The Illuminae Files, but AIDAN is there. If you haven't read the series, AIDAN is a robot with a tendency to commit mass murder. The novella is about AIDAN's creators and first victims.

Is it weird that I enjoyed the novella more than a few of the books in the series? Maybe I just love novella-length books. They cut out all the fluff. This one is short and snappy. Like the rest of the series, it has twists, and unique formatting, and morally gray characters. If you enjoyed the rest of the series, it's definitely worth reading.