A horrible waste of time and dead trees. If this was an episode of a Trek television show, it would have been a "clip show". You know, the ones that recycle footage from previous episodes to make up the majority of the content. Often this comes in the form of flashbacks, "remember when". Usually this is to save on a season's production budget. Wonder what the excuse was for this novel.
Well, that's what most of this book was. Remember when. If you cut out all of the clips, you'd be left with a short story about some Bajorans, an assassination, and a description of the new DS9 starbase. So... about 50 pages or so.
The novel was not mostly flashbacks - the Kira side of the story alone was at least 100 pages. Really the only flashbacks that I can remember are Kira watching "Emissary".