My daughter became a vegan after reading "Fast Food Nation". She'd always known where meat came from, and she'd eaten it more or less willingly until she was 13 or so. Reading about how cows, pigs, and chickens are often mistreated turned her right off, and she hasn't knowingly eaten meat since.
The brain-hurty part is the people who don't understand her reasoning. I think they envision all farms as wonderful, bucolic places with frisky lambs and happy smiling pigs, and they can't or won't acknowledge that she might have a point.
(This isn't intended to insult anyone who owns a farm, and I hope I haven't given offense.)