I'm also wondering the same thing: they should specifiy that the trade book is really offset printing, and should clearly specify if

they can offer digital printing for a price if requested.

My previous 2 books printed were excellent quality (First book 3 years ago and second book over 1 year ago).  The book I have just received is VERY DARK yet the photographs used were either the same or better quality than what I used in the first 2 books.  The entire book is dark, even the photographs taken by professional photographers.  I paid extra for premium papers and picked the top quality options, thinking this book would be even better than the first 2 but have been really disappointed with the poor quality result.  I don't think BLURB have any quality control - this should have been communicated to me prior to printing as nobody would like to look at this very dark book the way it is.  I am hoping they will do a free reprint and lighten their printing process for a better result that is more true to life.