Some books I write with Midnight Sun Brain and some with Long Night Brain. I can feel the difference. I don't expect it to be sensible externally, although people who know me might be able to guess which books were which from here. No points for guessing that Thermionic Night is a Long Night Brain book. Equally no points for guessing that Midnight Sun Rising will be a Midnight Sun Brain book. But once the latter is written and my lovely first-readers have read both, they might be able to guess the rest from there.
I am beginning to think that second books in series are always Long Night Brain, regardless of whether the first books in those series are Midnight Sun Brain or Long Night Brain books. I think it's part of second-book nature. So far I've written the second book in a four-book series and the second book in a trilogy, and I'm currently writing the second of what will probably be five. And they're all Long Night Brain books. Thinking of other people's famous second-in-series stories, The Two Towers looks from the outside like a Long Night Brain book (so does the rest of LotR), and "The Empire Strikes Back" is definitely a Long Night Brain movie, but Prince Caspian was a Midnight Sun Brain book, so probably this is just me, if that.
If I have no particular reason not to, I should probably write a Midnight Sun Brain book next just to keep the brain from going too very lopsided.
It's all about where the light goes, really.
Ummm. Anyone else have professional bits of externally incomprehensible fruitbattery they'd like to share?