I see you abandoned filter objects. Good, they were confusing, too complicated and unneeded.
Why is the errata not included in the book or even needed for corrections can be made as they arrise?
Why keep old drafts when the book is inclusive and upto date?
Were it in TeX, the mathematical standard of today, it would be much easier to manage, read and comment. According pdf delays and slows down the utility of your writting. Abobe readers are barely useful and pdf composing software too expensive.