don't think, just write

Continued fixing next-to-last couple of chapters. Probably tomorrow I'll try to get that very last one into some kind of readable shape. That's going to be tough--but maybe, with luck, sometime this weekend I'll be far enough along do a readthrough of the second half of the book to see if the big picture is working. I've read over the first half too many times already, so will save that for one last beginning-to-end readthrough, once the second half is coming up to par.

If the big picture is not working, I'm pretty much screwed and will have to set the whole thing aside for a while. Which would be disastrous, so it doesn't bear thinking about right now.