Serus
Arcane
I want to add that if we claim that books with any kind of FTL are "fantasy" then half of the most famous sf writers, including many that are considered authors of hard sf, wouldn't be ones. Just think about it for a moment, i had a list but i won't help you being lazy, just go trough some of the big names in sf. Basically any sf that wants to explore possibility of life on other planets in other solar systems, or any kind of encounters with extra terrestrial intelligence would be "fantasy". Unless someone wants to play with sub-light interstellar travel but that also is questionable from science pov. That is insane, would make the term "fantasy" completely useless.
A book that contains one or two concepts that are scientifically questionable and then 90% of rest of the book is undoubtedly great sf, even hard sf, is still SF without a doubt in my mind. FTL as in starships simply accelerating beyond speed of light is fantasy because we do know (or at least we think so) that it is impossible. But treating the exact same way every other hypothetical way would make exploring so many other classic SF themes impossible. It is not even funny.
A book that contains one or two concepts that are scientifically questionable and then 90% of rest of the book is undoubtedly great sf, even hard sf, is still SF without a doubt in my mind. FTL as in starships simply accelerating beyond speed of light is fantasy because we do know (or at least we think so) that it is impossible. But treating the exact same way every other hypothetical way would make exploring so many other classic SF themes impossible. It is not even funny.