Gideon the Ninth
The first book of the Locked Tomb series finds Gideon Nav posing as the Cavalier Primary to Reverend Daughter Harrowhark Nonagesimus as they face trials to serve the Emperor Undying.
This series is wonderful and nuts. A space fantasy with lesbian romance, gothic swordfighting and horrific undead monsters.
Filled with beautifully seeded worldbuilding and a wicked terminally online sense of humour.
I straight up loved this book.