I've only just realised that I initially intended for Chapter 12 to serve as the final chapter in Book 1. Looking back on it, that seems pretty laughable now, what with me not being entirely sure I won't end up writing a Chapter 14 as well.
The good news is that I am able to have stints of uninterrupted writing, and I'm making consistent progress. So, regardless of whether we ultimately end up with 13 or 14 chapters, things are moving forward steadily.