Ohhhhh you're doing Queen's Thief reviews, I'm excited! It's been long enough since I first read The Thief that I'm not sure if I picked up that Gen was the Queen's Thief or not, but I did have the mistaken impression that he was a girl for the first part of the book (I think I had read some other book where the main character also started out in prison, and was a girl, and mixed them together in my head). I spend a lot of time hanging out in a discord server for the series though so I can tell you that there are definitely adults who do not pick up on the twists on their first readthroughs...we are all constantly bemoaning our lack of reading comprehension, haha.

Anyway I'm excited to read the rest of your reviews, and also to see what you think of Return of the Thief when you get to it!