Nostalgia is something we think of as fuzzy. But it's pain. Pain concerning the past.
The great thing about using the past is that it gives you the most colossal freedom to invent. The research is necessary, of course, but no one writes a novel to dramatically illustrate what everybody already knows.
I don't separate my books into historical novels and the rest. To me, they're all made-up worlds, and both kinds are borne out of curiosity, some investigation into the past.
