Basic Trope: A character the audience is supposed to see her/himself as.
Straight: Elina, a main character in Mysteries of the Fantasy Romance has no description on her looks and lacks personality and the story is told in first-person so girls can imagine themselves as her.
Main character doesn't even have a name for that purpose. In fact, you can order a special-made edition of the book with your name as a main character.
Inverted: All the characters are described very accurately and their personalities and looks are made so that the audience don't even think of imagining themselves as the main character.
Subverted: Elina actually gains personality traits and looks will be described as the Mysteries of the Fantasy Romance series goes on.
Double Subverted: It turns out that where Elina's looks and personality was described, was just a dream.
The main character is named Acharacterthe Readeris Supposedto Seeherselfas.
"I had the weirdest dream; I had a personality!"
Zig Zagged: ???
Averted: Book writer doesn't bother to make the book to have characters you can see yourself as.
Enforced: The writer is writing an escapist book and wants the audience to escape into the book as one of the characters.
Lampshaded: "So, dear reader, how are you enjoying the events happening to you in that book?"
Invoked: Elina's life is very dangerous and she's trying to think of ways to avoid dying. Therefore, she tries to act like someone who'd be reading her own life story, reasoning that an audience stand-in would be very unlikely to be killed off.
Deconstructed: The main character in the book slowly realizes that she has no true identity of her own and feels that her life has no purpose.