People are much more complicated in real life, but my characters are as subtle and nuanced as I can make them. But if you say my characters are too black and white, you've missed the point. Villains are meant to be black-hearted in popular novels. If you say I have a grey-hearted villain, then I've failed.
I went and looked at one of these great cathedrals one day, and I was blown away by it. From there I became interested in how cathedrals were built, and from there I became interested in the society that built the medieval cathedral. It occurred to me at some point that the story of the building of a cathedral could be a great popular novel.