Board Thread:General Discussion/@comment-82.43.138.194-20140707202022/@comment-25204559-20140813035453

An anime is also a different "variant" of whatever it was adapted off of, since there could be a manga and novel series along with it, all three with differentiated events, characters, and certain points of the plot. Whatever came first though, the original, would probably be the most reliable source (in this case the light novels, and seeing a shelf of ggo-arc novels in Japanese in a manga store doesn't exactly make me happy :/)