Not important to send, but I prefer to export a PDF first. The exported PDF will be identical to what's shown on Blurb's web site, and I have previously found small discrepancies between what was shown in LR's Book and what was sent to Blurb - I think those bugs were fixed. Secondly I like to review the book when I'm mentally fresh, so I'll put the PDF on the iPad and look at it later.
Also, consider softproofing images in Develop using the sRGB profile. Not perfect, but I'm not sure one can do better in LR.