At first, I was concerned that these stories would all wind up being more like young adult romance because the first two stories reminded me of this. A young man falls in love with a prostitute and is willing to sacrifice his integrity to win her. A young woman is in love with a man below her station while betrothed to an older man who practically repulses her. Such stereotypical tales, especially in young adult romance, are what greet you with the first two chapters. It occurred to me that one of the first two stories is indeed written by a young adult author though so I guess it's not surprising.
But the first two chapters wound up being more like a lead up. Unlike other short story compilations where each story may be set in totally different years, these tales are told chronologically so the first two stories are mostly set in the days before the eruption and the latter stories start at the beginning or in the middle of the destruction falling around everyone. The built up carries through the whole book, rather than there being a build up in each story. This too gave it more of a novel-feel than a collection of short stories.
It's also very impressive that this many established authors were able to collaborate to come up with overlapping characters and well written, interwoven stories. It was much more than I expected it to be.