These are some of my favorite and most intriguing completed longfics and unqualified recs that I've read in the past few years:
I'm guessing you've probably read Pride Is Not The Word I'm Looking For by Tossawary - long long meaty SVSSS fic that asks 'what if Shang Qinghua DID interfere in the plot?' if not, you should definitely check it out! Really great at worldbuilding and at following through the logic of the world and the system and SQH's own nature, tight engaging plotting, Moshang pairing (though I would consider the romance a side plot here rather than the main thread, which follows the canon divergences SQH sets off and his -and other people's- struggles with them). archiveofourown dot org works/25997320/chapters/63206428
Less well-known svsss fic that is also excellent: Tarnished Gold by Prim-the-amazing. archiveofourown dot org /works/48752503/chapters/122981467 Another well-plotted, tightly-written character-driven what-if story: Shen Yuan transmigrates into Gongyi Xiao. What happens when Binghe crawls out of the abyss and begins his campaign to take over Huan Hua Palace? It's Binghe POV so the perspective gap between what he knows and what the reader knows as Binghe tries to puzzle out SY's behavior is really fun. It really hits that sweet spot of being unafraid to let characters be themselves, including their worst selves, but still sticks the landing in making the happy ending work. This one is Bingyuan. Also does some stuff with Huan Hua Palace internal dynamics that I really loved!
Stepping outside of SVSSS fandom: Baba by CrownofPins for Castlevania (netflix adaptation). Conveniently written after season one so you really only need the first season or basic familiarity with the concept to enjoy. I think I watched Castlevania for this fic. Very sexy ot3 UST-that-resolves, snowed-in-a-cabin-and-things-get-magical-and-mysterious story. Cosy, hot, intriguing, and with some fun whump if you're an aficionado of that kind of thing. If you liked casefic at all in the SPN fandom days, I think you will like this too. Like PINTWILF, there are a number of other smaller fics set in this universe so the fun isn't over immediately. archiveofourown dot org /works/11544798/chapters/25923672
If you want something with a historical and romantic flair, AMarguerite has written quite a few truly excellent Jane Austen longfics. It is a high bar to be able to satisfyingly write about or pastiche Austen's characters but AMarguerite clears it. If you're feeling more romantic comedy of manners, An Ever-Fixed Mark (archiveofourown dot org/series/629375) is a deconstruction of the soulmate-identifying mark trope with a bunch of fun related spinoff fics; turns out having a name appear on your wrist does not in fact make the marriage market, or finding love, any easier. If you're leaning more towards adventure and action and dragons with your romance, A Monstrous Regiment and it's sequel, A Nobler Ambition (archiveofourown dot org /series/1004649) mash up Naomi Novik's His Majesty's Dragon universe with Elizabeth Bennet as a dragon captain in the Napoleonic wars. Full disclosure, I hadn't read any His Majesty's Dragon when I first read this and was iffy on my recollection of the Austen too. Still had a roaring good time. Some good classic battle couple action in the sequel.
Finally, if you're willing to take a walk on the scifi side with transforming robot aliens, The Echo Garden by AltraViolet (archiveofourown dot org /works/22553779/chapters/53895550) got me into a whole new fandom. This one I went into with only a broad strokes knowledge of the canons and it worked out fine. Crossover 'crackship' between the silent, spooky Decepticon lieutenant Soundwave from one version of a Transformers show, and the brash Autobot captain Rodimus from a totally different universe of a comic run. I picked this to read not knowing the source material very well because I wanted a really good character-driven 'evil guy learns to change his ways and care about others kinda despite himself ' story and boy it delivered. The ship's crew, ensemble cast, and the bonds Soundwave eventually builds with many of them is a real standout highlight of this fic, along with the romance (which is a long time coming, and slow burn when it starts to appear, but very very satisfying. Also, some surprisingly hot robot sex?) It's fun seeing them get to a place where they actually really work together. The author took the premise of 'what would it take to make these characters 1) meet, 2) see value each other, 3) fall in love, and 4) get together?' very seriously and the result is just a really thoughtfully executed story - a very satisfying example of what fanfic can do by asking 'how could this scenario or pairing happen?' and then proceeding to build a fantastic flight of imagination. This is also a pretty plotty story with lots of episodes of action and space travel worldbuilding and other events - even though it's very long, it does not drag its feet at all. There's also some fun multiversal scifi - Soundwave is not the only version of a character from an alternate reality on board. This is the phenomenal fanart that made me check it out: tumblr dot com /altraviolet/761812421416468480/wow-thank-you-so-much-for-all-these-beautiful
All of these fics are in the 100k-400k words range and complete; I hope you get a chance to check some out, and have a good time on your trip!
WOW WOW WOW WOW WOW!!!! These all look FREAKING AMAZING, thank you for directing them my way!!!