In "Sweet Sam", we read about a brother that takes a vacation from colder weather to warmer, meeting up with his sister down in Florida. While talking about fantasies, they end up exceeding even their "nastiest" one.
The sex in this story had some nice build-up. From words to physical acts, the interaction was good. It isn't scorching, but it works fairly well.
The plot itself is pretty basic, but that isn't surprising in a fairly short story. The author's protagonist did tend to think the same thing a few times over, making for a few "um, you already said that" stretches. Also, he indicated (several times) how open they historically have discussed their sex lives, fantasies, and previous lovers. Yet they apparently have a first time discussion about masturbation, which didn't make sense.
Technically, there were a few typos in the story, that were only minor distractions.
Overall, the story is good for some decent stroke if you are into bro/sis incest between adults, with good build-up to the actual act. The repetitive nature of the early part of the story took some of my enjoyment away, as I felt like I was starting to read "Groundhog Day". Once it got past that stage, it flowed pretty decently, but I had already lost some steam.
This one isn't great, but it certainly isn't bad. A little better than your average incest story, but not by much.