When a novel is based off of a TV episode, one needs to look further then the surface story. The Emissary did not disappoint in this aspect.
The novel included a bit more more than the episode showed. One might consider reading it if you never saw the episode, or if you would like to read it more in depth. For example, the story includes extra moments showing how Sisko almost left Deep Space Nine soon after he was first assigned there.
The author deserves compliments on how they handled the "wormhole aliens". This was the first time I had encountered them, and suffice to say, they could be a bit confusing to read about if you do not know what to picture. However, the author did a great job of explaining this aspect - which is a major part of The Emissary.
Overall, this is a fine read for either the die hard DS9 fan or one who is introducing themselves to this Star Trek spin-off series.