Bingo!

At last!
I have been through the book and weeded out errors....
I have transcribed nearly all of the new interviews...
I have worked out which sections are going to have new material inserted into them...
And
I have started writing! 30 very fruitful minutes this morning, more than that tomorrow and the next day and the next.
What a puzzle it had seemed, how to crack into a sealed book! But I know what to do now, and it's going to take me two weeks to finish it, I think, I hope.....