The book ends about 18 months post-Unity (the O'Brien's are in 'their second year on Cardassia Prime', The Lotus Flower (which is two months after Unity) took place 'over a year' ago, and then there's a fair amount of travelling between Earth (a visit there of several weeks), Bajor, and Cardassia which must take up a couple of months). This puts it sometime in early 2378, the (current) latest timeframe for the DS9-R.
I mostly enjoyed the book, but felt it lost its way a bit after Rugal was forcibly enlisted in the military, and was taken off Cardassia Prime. Up until then, it had been an interesting look at how the civilian population of Cardassia dealt with the events of the series, but that perspective was almost completely lost as a result of that plot development - the characters we had dealt with were (with only a few, rare exceptions) never heard from again, and I felt that the novel lost some of its strength with that move. Still, a fascinating look at Cardassian culture and philosophy.