The Lightroom Book module PDF exporter works well, unfortunately it does not produce a file format that can be accepted by Blurb if one wants to upload to their site directly (ex. when LR hangs trying to upload as has been experienced by myself and others). Blurb requires PDF/X-3. Many won't have the ability to convert the existing file. Offering this format at least as an option would give users a backup option to get books to Blurb.