Just updated to version B4.0 that says “content complete”. At 153 pdf pages the book does not really cover “Modern Vim”. A reader (unless vim expert already) needs “Practical Vim (2015)” by their side to actually learn how to use vim.
To me Modern Vim book looks like several new chapters that should be added to “Practical Vim 3-rd edition” or “Modern Practical Vim”. This would had made a much better and complete book!