Star Trek: Mirror Universe is a prose fiction series set in the mirror universe featuring characters from many Star Trek series.
It began with a series of six novels published in two books in 2007. The books featured one novel for each of the five television series plus the New Frontier series. In 2009 the series continued in an anthology of twelve short stories, Shards and Shadows, which included stories from several prose only Star Trek series. The most recent book in the series is Rise Like Lions, a full length novel by David Mack.
The DS9 relaunch novel Fearful Symmetry was also planned to be released as part of the series according to early cover designs, but the final release, while partially taking part in the mirror universe, did not feature the Mirror Universe banner. The Soul Key also ties into Star Trek: Mirror Universe.
According to the former e-book editor Keith R.A. DeCandido and editor at the time for the Star Trek line Marco Palmieri, there were plans for a mirror universe Star Trek: Corps of Engineers ebook to be released at the same time as the anthology Shards and Shadows. Unfortunately the original e-book line was put on hiatus before that time and as such the CoE story was cancelled. The story could not be added into the anthology itself as there was not sufficient budget to add a thirteenth story at that stage, so CoE remains unrepresented in the Mirror Universe series.