The Mirror Universe Reading List is centered around the series of novels fleshing out the history of the mirror universe, specifically Emperor Spock's Memory Omega movement. In addition to the main novel line, one short story is also connected, from Seven Deadly Sins.
Eleven other Lit-verse linked novels are connected to the mirror universe in various ways, though not always in continuity with the Memory Omega storyline, and are included here: Discovery: Die Standing, Stargazer: Three, The Next Generation: Dark Mirror, Spectre, Dark Victory, Preserver, Deep Space Nine: Warpath, Deep Space Nine: Fearful Symmetry, Deep Space Nine: The Soul Key, Section 31: Disavowed, and Coda: Oblivion's Gate.
Several comics are also connected to the mirror universe in various ways through these comics miniseries: The Original Series: New Frontiers, The Next Generation: Mirror Broken, The Next Generation: Through the Mirror, The Next Generation: Terra Incognita, The Mirror War, and New Frontier: Turnaround. Though again not always in continuity with the Memory Omega storyline.
Dark blue denotes the primary narrative. Read these for the bare bones story. Light blue denotes the expanded storyline. Read any or all of these to go a bit deeper. White denotes every other connected story, regardless of overall continuity. For the absolute simplest story, read the essential duology.
As always, not every reference to every other story is mentioned, just the one I chose as most important to show the expanding Lit-verse web.