Dr-lurking to give a general example. I am one of the few people on the planet that hasn't religiously watched Big Bang Theory. I knew of it and had enough familiarity of it to know the first names of the characters.

When bored one day, I went searching for fic. I picked a long fic that was complete. It turned out to be a Sheldon/Penny story which today remains one of my favourite stories.

If the story is good, you don't need in depth familiarity with all of the canon.