If I may plug slightly, the current second edition of the book can be had here:
Writer, Author, Hiker
www.kenmacgray.org
As far as what gets added and removed, OTHH evaluates the list every five years. This was last done in 2020 so the next possible changes will be in 2025.
Unofficial trails like Fisher and bushwhacks like Eagle Cliff won't qualify. The "guideline" is that each hike needs an official trail to a view, but that view doesn't necessarily need to be a summit.
Some peaks will never make the list because they are too low (looking at you, Mt. Major). The general elevation threshold on the low end is 2,500-ish, but there are some exceptions now.