I have to start with a content warning.
The Winter Boy contains a lot of sex.
Fairly explicit sex.
Between a woman in her early forties and a young man who's age isn't specified, but who can't be more than 18-19.
If that squicks you, then...well...you won't want to touch this.
I couldn't put it down.
I literally could not put it down. I haven't been this drawn into a book in a while, and it's not because of the sex.
Grotta builds a world that may or may not be our world (It's definitely post-apocalyptic). Peace is preserved by the Allemen, specially trained men who act as diplomats, mediators, judges and, when all else fells, warriors. The regime is trying to spread further, out into the world. Unfortunately, they're facing an implacable enemy named the Mwertik Zalog - who seem bent on destroying them and their way of life for no reason.
Then she introduces herself to Rishana, an Allesha - one of the "Every Woman" figures who trains the Allemen. With sex. I know I keep harping on the sex, but this book falls within a broad definition of erotica. Apparently, in this world, teaching a man to be really good in bed helps him learn to be sensitive, diplomatic and aware in other situations. (There might be some truth in it). And now she's training her first Alleman - a difficult boy. And one with secrets that might hold the key to defeating the Mwertik Zalog.