Landgraf revealed at the TCA winter press tour that the new season will be "completely different" than previous outings, reported Ace Showbiz.
"I know what it is, but I can't say. I have to let series boss Ryan Murphy do his thing on that. But it's very different," Landgraf said.
"One of the things I love so much about that is that it can be radically, radically reinvented in terms of tone, setting, period, characters, cast.
"I think there's going to be an unusually large reinvention in between Book 4 and Book 5 relative to, say, between Book 3 Coven and 4 Freak Show."
"Ryan is really, really independent in how he makes these shows and what he does. So I know the setting, I know something about the characters and something about the tone and the time period, but I don't actually know the cast yet," he said.