Definitely my favourite story from FW, and one of the best Mom NTR stories out there, in my opinion.
Loved the flirtatious nature between the mother and son throughout the story, even when it was intruded upon by Richard. What made this story especially cruel was how there was a tug-of-war going on for the mother's affection, and for every time Lawrence was able to slightly pull Monica to his side, Richard would gain that ground back and then some. It was a twist of the knife that really sunk in the son's despair and his losing battle. It's clear that the mom does want to dote on and care for her son, but the cock of that little shit is just as persuasive. The descriptions of the mom and the sex scenes just ooze off of the page, as well. I was following along from the incomplete portions offered by UF, and I would've been satisficed I think if either Lawrence or Richard won.
If I could mention a slight critique, it would be in the last few pages of the conclusion. We are given hints that Richard impregnated Monica, and while this is often the eventual conclusion of many mom NTR stories, I'm not sure if it quite fits with AMS. The want of a pregnancy isn't ever brought up earlier in the story, so it comes up out of nowhere simply as a thing that typically happens with enough sex. Richard also comes off as a selfish, monopolizing runt, and who is a highschooler that would hate sharing Monica's body with anyone, even his own baby. I would've perhaps suggested an alternative stinger at the end, instead. Marriage would've been one idea, but also would come out of nowhere. How about Richard changing his legal address to Monica's home? Sure it's not as sexually charged a reveal as pregnancy, but is more thematically appropriate to this story and is easily something that Richard and Monica might've tried and hide from Lawrence.
That's just a nitpick, though, and is only something that effects the tail-end of the story. Overall thought it was incredible, and will be coming back for rereads many times I'm sure.