I came across this question in the blurb forum, which i had to perform myself for one of the albums i was working on.
forums.blurb.com/forums/4/topics/3868
In general How can i update the photos in booksmart to use the latest updated photos that i have edited in photoshop/gimp?
You can delete the files in C:\Documents and Settings\{USER_NAME}\My Documents\BookSmartData\{BOOK_NAME}library.
In booksmart, [...]