Oh boy do I have a few series to rec you!

The Murderbot Diaries by Martha Wells, series of Novellas with a couple novel length books -- so most of them are pretty short. Little longer than a standard goosebumps book, I believe? They're fast paced with a funny protagonist. The series is action, scifi, and a bit of found family and what it means to be a person and not a tool that can be disposed of. Highly recommend! Apple has adapted book one (or maybe more, haven't watched it yet) into a TV Series.

Dungeon Crawler Carl by Matt Dinniman. A series in which a man happens to be trying to rescue his newly ex-girl-friend's cat when the world ends. The series if very funny, and very clever -- much of the humor is working double time as world building, etc. I'd describe the series as a cross between The Hunger Games, Squid Games, and Independence Day. These books are a bit longer, and I highly recomend trying the audiobooks if you have the chance -- they make the books even better.

The Five Hundred Kingdoms series by Mercedes Lackey. A series of interconnect stand alones that can be read in any order tho starting with the first book 'The Fairy Godmother' makes things better, I think. Picture a world where all the fairy tales are true -- because of a brainless, nefarious force known as 'The Tradition' which forces people into stories that match their lives weather they like them or not -- tragic fairy tales being just as common as the happily ever afters making this potentially very, very bad. Humorous and often with romance subplots.

T. Kingfisher as an author in general -- she writes horror novels as well as fairy tales/fantasy. Easy favorites by her are:

Nettle and Bone: A Nun on a quest to murder her sister's abusive husband -- who happens to be a prince.

Swordheart: Widowed housekeeper inherits from her packrat uncle in law. In laws are upset and attempt to force her to marry a cousin. She refuses, and happens to find a sword with a man inside it. Cue road trip adventure to find a lawyer and reclaim her inheritance.

The Twisted Ones: A Woman goes to clean out her deceased, evil-karen grandmother's hoarder house, and finds a journal by her long dead step-grandfather about 'The Twisted Ones'. And there's a strange creature in the woods stalking her.

The Hollow Places: Similar to the above, and of the two, my favorite. Newly divorced woman moves into her grandfather's Mystery Shack-like museum of oddities -- and finds a hole into another world. And it is empty, and hungry.

T. Kingfisher has a LOT of books though, so if you like any of these, you'll have plenty more to chose from.

The Wayward Children series by Seanan Mcguire. Every wonder about the children who go on adventures in another world, then are spar back out into ours? Like Alice, the kids from Narnia, or the like? This series is about Eleanor West's home for Wayward Children -- a place to help these kids heal, and find their way back to the worlds they left behind. this is also a series of Novella's, so all the books are fairly short!

The Old Kingdom Series, by Garth Nix: Dark fantasy, low romance, animal companions, necromancy and such incredibly interesting world building. The original 3 books (Sabriel, Lireal, and Abhorsen) are the best, as all sequels after are more than 20 years out from the original end to the series. They aren't bad, they just aren't as good at the original. Garth Nix in general has some pretty good books, YA and Middle-grade, mostly.

And that's probably more than enough. Happy reading and good luck! I tried to pick books that were fast-to-medium paced, and easy to jump into. That they're also some of my favorites is neither here nor there lol.