It seems that you've thought about the book situation very carefully and agree that timing is everything. Even if you do talk this week with W, I'd hold off on bringing up the comments as you said that things are "fragile" at the moment.
From my perch, it is more important to build up the communication channel with W. That is how trust is earned. Communication, validating, and consistent actions. These three prongs are a good bridge building to the piecing. I am not sure if you are in the piecing phase as it seems that W is not yet at that place or mindset in reconciliation. More of a "wait and see" approach to ensure that your words and actions are congruent to her. This is how you earn your trust with her. Make sense?
Oh and I would add that using humor during those talks are good way to inject light-hearted moments. Sometimes people get way too intense and they feel suffocated. It is a delicate dance that I think you can do here, GoFo! Self-deprecating humor is a winner!
If the kids weren't such an easy excuse I wonder how much harder it would be for us to interact.
Mindreading...forget this. Does not do you any good.
If the discussions go well and are healthy and about rebuilding trust I may mention the book comments and approach it from the kids needing to be safe angle.
This is all down to timing. You would want to build on any of the positive interactions so she'll have more positive thoughts and memories. You'll know when it is the right time.
Self-deprecating humor is a winner! 
