@rlh3 - it would be a bit too expensive/slow to do this I think.
However you do have another option (presuming you are already calculating these for your books). Select the books and export as a CSV catalog - you can pick the columns to include, include your #pages and #words columns in there. Then just load it up in Excel and you can get your sums. You could turn it into a pretty report if you wanted to, track progress etc...
