But it's not a rule. The only rule (if you want to call it that) in writing fiction is to be creative, and for some writers that means doing a lot of things different from book to book or writing outside of their potentially narrow plane of existence. Think about science fiction for a minute: if it's ok to write about someone from an entirely different planet, why isn't it ok to write about someone who is different from you in a much smaller way? Sure, aliens don't exist (that we know of) but neither does the particular character you are making up.
Many other lines are crossed by writers all the time. Authors regularly create characters of different genders, nationalities, sexual orientations, or classes than themselves, often with great success. Look at the female characters of Chris Bohjalian, the intersex character in Annabel by Kathleen Winter, or the angry teenaged boy who stars in A.S. King's Reality Boy. Maybe that's not every angry teenage boy's experience, but sure it's not unbelievable as some boy's experience. The character only has to be believable as someone who could exist, not necessarily mirror someone that you actually know, right?
I'm a librarian and it is somewhat inherent in my nature to fall on the side of intellectual freedom. As far as I'm concerned everyone has the right to write about whatever they want, using whatever words they want, to convey any idea they want. I like controversy, and taboo subjects, and politically-incorrect language. Yes, those things make people uncomfortable, but that isn't always a bad thing. Uncomfortable makes you ask questions and challenge your assumptions and start a conversation.
What do you think? Have you read any books in which author crossed these lines, and how do you feel about it?