I am actually closing in on finishing the rough draft of the book. I had the advantage that the book follows the lectures I gave for many years, so I could simply open the lecture notes and give the lectures one more time, this time typing rather than speaking to a class. I did get to check a few details. I expect that this week will bring me much closer to completion. The harmonic oscillator chapters, perhaps around 90 pages have had many of their proofreading and rephrasing bits inserted and the matching figures created and inserted. At that point I will likely let the book sit for a month or two.