Work on Book, 4 is proceeding well. 72 pages in and I ended up changing the ending i had planned out. I went for something more epic. Also came up with a better epilogue idea, that teases at book 5's villains.
May find myself stopping soon, though. Have to decide if the civil war ghost army would use their era's tactics in battle, or smething entirely new now that they's invincible spectres.
And dang it, the new plot calls for the destruction of not one, but two cool, multi million dllar aircraft. I hope that doesn't become a thing- destroying expensive equipment every book.