BookSmart takes a copy of the photos (giving them a unique name-number), it does not retain any link to the originals. So you will need to re-import the photos and paste them into the pages. Re-importing the photos is not enough as it will treat them as new photos.
The way I go about doing this is to drag and drop the updated photos from my directory straight into the image container on top of the previous version, it will then replace it. That works out quicker than importing then placing and also stops me getting muddled as to which is the updated photo in the My Photos thumbnails.
Having done that for a batch of photos I then select the Filter drop down in My Photos and deselect Show Used Photos and select Show Unused Photos, you'll then see all the replaced photos that are no longer in the book. You can then select all those and delete them.
Then remember to reset the filter - otherwise you'll panic thing that all your photos are gone - well, maybe you won't but I did once.