Using CMYK images in Booksmart
As you may have already discovered, Booksmart will not accept CMYK images. This is a problem because if you submit your images in the original RGB format, you will no control over how they look after they go through Blurb’s process for making the files print-ready.
My solution for this was to convert all the original RGB images to CMYK, then do color-tweaking as desired. Then convert them back to RGB before uploading them to Booksmart. This way you can be sure they will still be consistent with the CMYK palette.