Looks like a valuable book! It's wonderful that this dialogue was possible and is available to readers. Many thanks to all involved.
Comparing the authors of this new book with those of the original 1999 book, I would guess that YEC is insisted upon by Ken Ham more than it was by Moreland and Nelson, authors of the YEC chapter in the 1999 book.
As far as science, perhaps evidence for an old Earth was about as overwhelming in 1999 as it is today.
Evidence for the shared ancestry of humans with other animals was likewise already overwhelming by 1999 (actually well before then) but perhaps not quite as accessible/understandable to non-biologists as it is today.
In any case, the four authors are each clearly leading champions of their respective positions.