Red X by David Demchuk is fiction mixed with autobiography.

Twenty-One Truths About Love by Matthew Dicks is a novel told entirely in list form.

I didn't care for either book, but they were definitely unique structures.

How High We Go in the Dark by Sequoia Nagamatsu was great and has been compared to Cloud Atlas, if that kind of structure is appealing to you.

another older recommendation is jacques the fatalist, where jacques is attempting to tell the story of his lovelife but is constantly interrupted by other people telling their own stories, there is a "reader" who interrupts the narrator to ask questions, and the narrator at times gets bored of telling the story and asks the reader to fill in their own details. it also has an entire section directly from tristam shandy near the end.

not sci fi or fantasy but worth a read if you have the patience.

It’s not sci-fi, but Hopscotch by Julio Cortazar lets you decide in what order to read the chapters.