The writing is absolutely delicious, and even though it's a Snape/Lupin fic, there's also Snarry involved. The prompt the author chose was "Snape captured/enslaved by Harry, and rescued by Remus" and boy, does it deliver! The sex scenes are lush -- there's one description that I *still* can't get out of my head, and it is nnnggh! -- and the narrative style and POVs are expertly done. Also, there's a twist in the tale that Alfred Hitchcock would have been proud of.
I'm not sure why it hasn't been read and reviewed more -- honestly, it's a sin that something this good should go unremarked upon -- but possibly the warnings put people off. Yes, there is a warning for non-con, but I felt it was dub-con at most, and I think it's unlikely to outrage anyone's sensibilities. It is on the darkish side of things -- someone described it as "murky" rather than dark, which I think is about right -- but please don't let that stop you. It's just a magnificent piece of writing.
The other rec is for Dark Lanterns which is a double-whammy of both art AND fic. It's Whore!Snape with a bit of cross-dressing, and a Lupin that is more wolf than man: hot,horny and foul-mouthed,like you've never seen Lupin before. It's just... GUH! Really, check it out, you will NOT be sorry. Here's the link: http://snupinsanta.annex-files.com/viewstory.php?sid=84
Both fics are gloriously NC-17, and both have luscious Bottom!Snape. Go try them out, and if you enjoy them, remember to leave the author some commentary, even if it's only one or two words. Enjoy!