I see more talk about NG+ and have to keep reminding myself to temper expectations >>
It's not anything that mindblowing, sadly
1. Port book 1 to Book 3's final engine, so it gets stuff like the improved paths, rollback, all the enemies, etc
2. Update the script to respond to you finishing book 3; most of it is simple enough (remembering names, remembering some choices you made) and write slightly different dialog for a couple of events
3. Some minor visual upgrades and fixes.
4. New events that trigger for anyone playing book 1 from scratch
5. New events that will only trigger for someone playing book 1 by starting from Book 3's end savegame.
#1 and #2 is done. #3 will continue for a while. I've got #4 and #5 to go, as well as various bug-fixes.
But at the moment I'm back on Morningstar; finishing up the rather crowded space between day 35 (Katie's fight) and 40 (MC's second fight). It's live on the Beta branch, but I still have some side-events to finish this weekend.