Yeah, that "Mortal Instruments" series is literally just Harry Potter fanfic with the names changed. If I rightly recall, I think the author (or one of her friends, who gives a shit since they're all basically the same person anyway) at one point also tried to sell a smaller story series. It was hilarious because the premise was "okay so like, imagine if there was like... a guy, right? And he wanted to save the world but then someone ELSE who was like, the chosen one... right... well like that OTHER guy saved the world and he was super upset about it! And they get together and make out and feel better!" and it was very obviously some Harry Potter shit with new names and all the context removed. I loved reading the pitch because it just underlined how fanfiction completely needs the backbone of someone else's world- and character-building to support itself. Without it, you get a lot vague preamble and characters we don't know or care about.