1. Fandom Category: Harry Potter
Pairing: Tonks/Lupin, Sirius/Emmaline
Fic Title: Nymph Vs. Wolf and Nymphadora's Wolfe
Link: http://www.fanfiction.net/s/2571997/1/Nymph_vs_Wolf and http://www.fanfiction.net/s/3222395/1/Nymphadoras_Wolf
Rating/Warning(s): PG-13/PG; AU for the ending of book 7, but there are spoilers through that novel.
Genre: Friendship, humor, romance, AU, Action/Adventure, plotty, long.
Why This Must Be Read: I can't really separate the stories as they're sequels and lead directly from one into the other. I absolutely love these stories because they're juts so charming. There are several "the book happenings from Tonks and Lupin's perspective" series (I'll even rec a couple below) but this one is probably the most cheerful of the lot. Moreover, this has Whimples the vorpal bunny and there is nothing funnier in this universe than the Remus vs. Whimples competition. Honestly, this series will just make you smile, laugh, cry, and be incredibly glad you read it.
2. Fandom Category: Harry Potter
Fic Title: He Was Never Loved So Blindly
Rating/Warning(s): NC-17; set prior to book 5.
Genre: Romance, smut, angst, AU, friendship.
Why This Must Be Read: I've not read another Tonks/Lupin story that utilizes this level of animalism on the part of Lupin. Which is a bit of a surprise, considering how often it's used in Lupin/other stories. Still, this story has wonderful language and very, very damaged characters. I think I like this so much because it feels so realistic. This is Sirius and Tonks and Lupin all mucking around in adult relationships and conversations and being more than a little lost in the process.
3. Fandom Category: Harry Potter
Pairing: Tonks/Lupin, Rose/The Doctor
Fic Title: Too Close to The Moon
Author: Lady Moriel
Rating/Warning(s): PG; crossover with Dr. Who.
Genre: Crossover, action/adventure, friendship, slight angst.
Why This Must Be Read: Because it's an incredibly good adventure story. Also, the characters are unilaterally spot-on. Basically, this is a great read.
4. Fandom Category: Harry Potter
Fic Title: The Great Shrivelfig Caper
Author: Bratty Jedi
Rating/Warning(s): PG; kidfic.
Genre: Action/adventure, friendship, romance, kidfic, post-series, AU.
Why This Must Be Read: Oh, this is so incredibly sweet. Not in an 'oh, god, get it AWAY', but in that it makes your heart feel all gooey and happy and pleased. You need to read this, if just so you can get the taste of the last book out of your head and revel in the what might have been. (Basically Remus tells a bedtime story.)
5. Fandom Category: Harry Potter
Pairing: Tonks/Lupin, Sirius/OC, others.
Fic Title: The Moon Series
Rating/Warning(s): R; violence. Also, there is a series chronology in the author's bio.
Genre: Action/adventure, romance, friendship, AU, angst, introspection.
WIP?: Individual stories are completed, but the series is ongoing, and the newest is unfinished but updated frequently.
Why This Must Be Read: Because the author's Tonks is absolutely amazing. This is the Tonks that we got glimpses of in the books and the one that I desperately wanted to get to know. All of the characters are well-realized, but the absolute standout is Tonks; and it's because it's her story. The author's style is lovely, and while she kind of steals the initial set up from the Stephanie Plum novels, she very much takes this universe and makes it her own. I love that Tonks has so many relationships with people; so many friends and so much family. I also love how adult both Remus and Tonks come off. And while I do have some issues with some of the choices the author makes, she backs them up and makes them work for her and her universe.
6. Fandom Category: Harry Potter
Fic Title: Amid My Solitude
Author: Sam Vimes
Rating/Warning(s): R; spoilers for book 6.
Genre: Romance, friendship, AU, introspection.
Why This Must Be Read: In the way that the previous series was very much Tonks' story, this is Remus. The reason you absolutely need to read this is because of the character voices. Remus, yes, but also for Harry. It's so rare to see Harry portrayed as the young man he is, rather than someone considered an adult. But at the end of the day, this is very much about Remus coming into his own, and learning to let people in.
7. Fandom Category: Harry Potter
Fic Title: A Star Danced
Genre: Romance, suspense, friendship, introspection.
Why This Must Be Read: This is courtship, plain and simple. It's two people liking each other, getting to know each other, and moving forward. This is what romance should be for each and every person. It goes without saying that the characterization is spot on, as is the language.
8. Fandom Category: Harry Potter
Pairing: Tonks/Lupin, Teddy/Victoire
Fic Title: A Little More Time
Author: Jess Pallas
Rating/Warning(s): PG; time travel! Spoilers for book 7.
Genre: Fixit, friendship, romance, AU, angst.
Why This Must Be Read: This is the ultimate fixit story. Basically everything in all seven books is canon, and this is Teddy Lupin doing everything that he can to know his parents. I love this because Jess is a phenomenal writer, but she's as much a grieving fan as the rest of us. The only difference is that she (like Teddy) DID something about it. And you know what? Hallelujah.
9. Fandom Category: Harry Potter
Fic Title: The Werewolf Who Stole Christmas
Author: Lady Bracknell
Rating/Warning(s): R; spoilers through book 7.
Genre: Romance, friendship, action/adventure, introspection.
Why This Must Be Read: I can't actually pin down one reason for reading this story. Lady Bracknell is one of the best Tonks/Lupin authors on the internet. This is chuck full of banter and friendship and what eventually becomes romance. It's just lovely. ETA: I've recently reread this entire story and I have to come back and kick my own butt. You want to know the reason to sit down and read this entire story? Because it's amazing. This is probably one of the best, fully realized romantic stories I've ever read. The characters are real, balanced people who make choices and live their lives. What's more, these characters FEEL real in ways that the original books never quite managed. No, they're not perfect, but they're not nearly as catastrophically stupid as they eventually come across. This is just so, so very lovely.
10. Fandom Category: Harry Potter
Fic Title: Shifts and Shades
Rating/Warning(s): R; spoilers up to book 6.
Genre: Action/Adventure, mystery, friendship, romance, long.
Why This Must Be Read: These two stories are the absolute be all and end all of realistic Tonks/Lupin. The are, quite seriously, amazing. They parallel books 5 and 6 and are basically the 'behind the scenes: what the adults were doing' versions of those novels. I've pretty much run out of adjectives that equate to 'phenomenal' and will end this with a "If you do not read any other story on this list, read these two."