I haven't read the book yet so I can't comment on the text itself, but I was just looking on B&N to see which The Fall book was next and when it was released and noticed there is not indication anywhere on the books that they are a miniseries or what order they are meant to be read in. So with that in mind, I can see where people might have gone into this expecting something more stand alone than what we appear to have gotten. I wouldn't blame any of this on DRG III though, this strikes me as something that would be more the fault of the marketing people than the writer himself.
EDIT: I was just looking around at the reviews on Amazon, and the majority of them are definitely more line with the negative comments here. It's definitely starting to hurt my anticipation for this, not enough to keep from reading it, but I'm definitely not as excited as I was before the reviews started coming out.