Mary Russell and Sherlock Holmes got married at the end of A Monstrous Regiment of Women. Not much detail is given to the act. More a statement that they did get married.
This little novella tells the story how it all happened. And, it's a glorious story, with both humor, seriousness and a trigger-happy cousin. Say what? You just have to read the story to find out! ;)
On a side note, I have read The Murder of Mary Russell and there are parts that brought a smile to my face thanks to the knowledge of the story in the book.
I hope you will enjoy this short novella as much as I did!