I'll list a few alphabetically.
Abby's Hope is a memorable story about about coping with pat traumatic stress. The protagonist does this by writing a fairy tale on that subject and then making an indy movie based on that fairy tale. The novel is presented in chapters which occur out of sequence.
I had a little trouble choosing between Arushi's two books set in India, but I think Beautiful Rebellious Brainiacs is maybe the more unique of the two. This story has so many twists that it defies categorization in any genre.
Chewing Gum is a fun little rock and roll romance about musicians which is currently being updated and rereleased by Valerie Diestro, so it is easy to get caught up.
Lost Number brushes a little close to the urban fantasy that you don't want, but I think it has several unique attributes. Set in small Japanese town, this horror tales stars high school students who are abducted by haunted public pay phones. To me, this feels like a cross between 80s Stephen King and the Persona video games.
Loyal at a Price is an action-packed sci fi story told in episodic style. The protagonist is a mercenary who holds strictly to her own personal code of ethics and thus the title.
Rock of Ages is simply the most fun novel on Tapas in my opinion. Leon weaves an epic adventure story set in the world of music album cover art.
Sphere of Calamity is a sprawling space opera about several cultures from different planets who meet on a remote refugee planet after a great disaster renders them all homeless. Swords, psychics, and spaceships
Lastly and very least, I shall link to my own story only because it is actually relevant to this thread. Alien Fiction is goofy nonsense. Roleplaying rules and non-canonical riff chapters are scattered throughout. https://m.tapas.io/series/Alien-Fiction