Release Notes:
https://github.com/kiwidude68/calibr...t_pages-1.14.2
The first new feature for a long time (thanks for the suggestion to Victor239 for requesting this ages ago).
Select a subset (or all) of your books in the library and choose 'Statistic totals for selected books'. This will display a popup dialog with totals and averages of pages, words and other statistic columns if you have them configured for those books.