The teenager thing: didn't have anything to do with Laurie King per se, but rather with the fact that at the time I read "The Beekeeper's Apprentice", I had just discovered a new fandom and, as always with new fandoms, had to wade through a lot of teenage girls popping up left and right to canon characters before finding the good stuff. Which is why Mary's age struck me. Call it an unfortunate coincidence.

You're right about marriage not being a necessary qualification for Sue-ness. But I think I might have continued the Russell books beyond No.2 if she hadn't married Holmes, or fallen in love with him. Because yes, a female perspective on Holmes could have been intriguing. As it is, the falling-in-love and marriage hit two of my personal squick buttons - the other being mentor/student relationships. (Which is, for example, why I don't read Giles/Any of the Scoobies stories in the Buffyverse.

Watson: let me just add it would have been possible, imo, to have Russell as narrator without mishandling or even retiring Watson.

One last aside re: Douglas' attitude towards Irene. She contributed a rather witty short story to a vampire anthology in which Irene rescues a chorus girl from the attentions of a vampire and is rather terse about the silliness of falling for aristocrats because of their looks and fancy titles and ignoring the obvious signs of something being wrong, while mentioning (the whole story is a letter to Nell) the charming Willie of Bohemia. Meaning: Douglas is kidding her character now and then, and I got the impression she also wanted us to see Irene as an egocentric. A charming, charismatic one, but an egocentric nonetheless (as Holmes is, too, another reason why Holmes/Irene wouldn't work out).