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The third story is interesting in that it is written as sort of a backstory to the Voyager series. In the pilot episode, Caretaker, viewers were allowed to see how Voyager came to get transported to the far reaches of the Delta quadrant. But we got precious little of the backstory of Chakotay, B'Lana, Tuvok and Seska as they were at the Maquis base and on the Maquis ship that Voyager was eventually chasing when both ships were transported. Wright gives us that backstory, plus throws in the troublesome microsingularity to boot. Just the sort of thing fans love in their fiction.
The fourth story is set during the portion of DS9 when the Dominion is about to align with Cardassia and invade through the wormhole. In addition, the Romulans are in the story. It has dramatic irony in that the readers know both the DS9 crew and the Romulans are after the microsingularity. Sometimes it is fun how Wright weaves it all together, sometimes it feels a little contrived (but one tends to forgive her).
So over the two books, one has a complete story arc regarding the microsingularity: how it got loose, the havoc it caused in the Badlands over the years, and what happened to it (although one thinks its disposition is less than perfect, and might even set up another story for someday down the road).
Wright is to be commended for getting the voices of so many characters from so many series down correctly. She gets the atmosphere of the four series right. Well done, ma'am.