I haven’t read much of the original books, I had no idea Mycroft was like that, that’s really cool!
I loved that particular instance too- when she didn’t speak to the audience, just kinda interacted with them in a sort of The Office way, was executed really well. Millie Bobbie Brown did a fantastic acting job, especially considering how different from her usual roles this was.
I‘ve heard that there’s at least some talk of a sequel, and consider the large amount of source material and the great reception of the movie I’m hopeful we’ll get another movie.