Hello,
This issue exists in the first version of the Briefing Book application.The next version of Briefing Book (available on June 26th, 2014) will resolves this issue.
If you receive the error "Updating of the selected items failed" continuously then the book has become corrupt. However, we can save your book. The workaround is to COPY the book. When you copy the book, the copied version will be created with the name "<your book name> -copy", in the book gallery. Go ahead and open this "copied" version and you will be able to edit and save your book once again.
-Lindsay