One characteristic is the blend of two different genres. It combines the imaginative and often futuristic or otherworldly concepts of science fiction with the emotional and relationship - focused aspects of romance. For example, it might have a love story set on a spaceship traveling to another galaxy.
The 'What's Mine Is Yours' manga is the origin. Adaptations try to stay true to its core, but sometimes they add or subtract details to make it more appealing or suitable for the specific format. It depends on various factors like the target audience and the creative team's vision.
Another popular one is '1984' by George Orwell. Although it's more of a dystopian novel which is also related to science fiction in some ways. It presents a terrifying vision of a future totalitarian society where the government controls every aspect of people's lives. The themes it explores are still relevant today.
I would recommend 'Foundation' by Isaac Asimov. It's a classic 'livre sciences fiction' that deals with the idea of psychohistory and the fall and rise of galactic empires. It's full of interesting characters and thought - provoking concepts.