See, the thing is, the best writers tend to write what they know. So if your super special talent is writing itself, then, well. Your books will surely be full of excellent, empty but superbly crafted prose.

The truly excellent pony-novels would come from experts in other fields, who just so happen to be literate enough not embarrass themselves. Whether their talent is storytelling, agriculture, magic, cookery or what have you, they will be the books that really catch ponies imaginations.