I think the best intro to SF is (was) the “Year’s Best SF” anthologies edited by Gardner Dozois. I haven’t found a replacement since his passing, but hopefully someone has picked up the torch with equal quality.

Science Fiction really shines in the short story form, letting the new idea in the story play out without wearing out its welcome. And for new readers, anthologies with various authors give an opportunity to sample many authors and styles quickly. Many SF authors work both in short form and in novels, so if you find a short story you like you can try the author’s longer work with greater confidence of making a good match.

The Dozois series also covered 30 years of SF, so it’s a great way to get a snapshot of various eras in science fiction if you’re interested in the history and evolution of the genre.