For example: A writer sets out to write science fiction but isn't familiar with the genre, hasn't read what's been written. This is a fairly common situation, because science fiction is known to sell well but, as a subliterary genre, is not supposed to be worth study—what’s to learn? It doesn’t occur to the novice that a genre is a genre because it has a field and focus of its own; its appropriate and particular tools, rules, and techniques for handling the material; its traditions; and its experienced, appreciative readers—that it is, in fact, a literature. Ignoring all this, our novice is just about to reinvent the wheel, the space ship, the space alien, and the mad scientist, with cries of innocent wonder. The cries will not be echoed by the readers. Readers familiar with the genre have met the space ship, the alien, and the mad scientist before. They know more about them than the writer does.
[...] This was literally proved when the first Harry Potter book came out and a lot of literary reviewers ran around shrieking about the incredible originality of the book. This originality was an artifact of the reviewers’ blank ignorance of its genres (children’s fantasy and the British boarding-school story), plus the fact that they hadn’t read a fantasy since they were eight. It was pitiful. It was like watching some TV gourmet chef eat a piece of buttered toast and squeal, “But this is delicious! Unheard of! Where has it been all my life?”
—Ursula K. Le Guin

Ursula K. Le Guin