Ok, so I've been messing with the html files, and it seems that adding <html lang="zh"> doesn't work...
So... I took a less elegant approach. I've taken the contents of a book that works perfectly and piece by piece replaced the contents of a book that doesn't work.
and yet somehow it doesn't work...
so... then I took two books that worked, and hit Tweak Book, then exploded and rebuilt them... and then they didn't work
