This wikipedia page needs work.
Science fiction – Wikipedia, the free encyclopedia:
Science fiction is a genre of fiction in which advances in science, or contact with more scientifically advanced civilizations, create situations different from those of both the present day and the known past. Although science fiction is often written primarily to entertain, many authors use the genre to provide insight into science, society, or the human condition.
I really don’t want to open up the “1984/Brave New World must be SF ’cause it deals with an alternative future” argument. Not because I care one way or another but because my beef here is with genres not a canon or collection of similarly themed books.
I say, “mainstream” the whole mess and let the reader sort it out. Ask a librarian or a friend who is well-read or at least know your tastes if you need something to read. Don’t rely on the marketeers at some publishing house.