Basically it's a call girl who got a job and when she got to the house she found out that the husband and wife are having their anniversary and all the meals and food was prepped and she was to serve them their five course meal (if I can remember correctly she wore just the apron as she was serving)
Then at desert the husband and wife start making passes at each other and this call girl starts getting involved and it turns into a threesome.
Can't remember too many details other than that and it's been a few years since I've read it. It's by far and away the best erotic story I've ever read or came across.
It was written in the point of view of the call girl, she was essentially narrating the story.
Thanks.
Source: reddit.com/r/eroticliterature/comments/35m5og/need_help_finding_a_story_i_know_next_to