Shariann Lewitt's sequel to her not-all-that-great-in-the-first-place Cyberstealth is a book that will pretty much be comprehensible, not to mention enjoyable, only to those folks who read and liked that book. I am guilty of the former but innocent of the latter, so I fear I cannot recommend Dancing Vac, though I did give it the old college try. Lewitt, at this early stage in her career, certainly had latent storytelling chops. But this book's rough edges are likely to leave your fingers badly scraped if not bloody.
Lewitt continues her saga of stealth fighter pilot Cargo, who has resigned his commission from the Collegium after it turned out that his longtime flying partner, an alien Akhaid named Ghoster, was a traitor. Cargo now ekes out a living in casinos, all the while feeling sorry for himself. Inevitably, he is drawn back in to his old life by a former fellow pilot, Stonewall, who wants Cargo to help track down and either catch or kill Ghoster. Cargo, however, still feels a strong tie of friendship and personal loyalty to Ghoster, despite the alien's crimes. So he decides to go along, but to save Ghoster, not kill him.
Cargo steals a merchant vessel and makes his way to the planet Mercanter, ruled by the enemy Cardia. He promptly discovers he's been set up; a power play, in which he is an Unwitting Pawn, is underway between his adoptive father, Bishop Mirabeau (who has been trying to broker a peace deal between the Collegium and the Cardia but who has strong personal political ambitions into the bargain) and Mercanter's devilishly charismatic, genetically modified ruler, Ki Shodar. A bewildered Cargo soon finds himself flying again, but on the side of the Cardia this time.
As you might have surmised from the plot synopsis, there is the skeleton of a potentially gripping military/political SF thriller in the making here. Trouble is, it's almost completely undermined by Lewitt's writing style, which seems to have been designed for minimum reader comprehension and enjoyment. Her prose simply doesn't flow. Lengthy, lumbering descriptive passages subtitute for dialogue much of the time. And since Lewitt also writes this novel with the presumption that you will be intimately familiar with her universe by having read Cyberstealth, much of what she's talking about in this story is barely intelligible. I read Cyberstealth two years ago and even re-reading my review of it failed to fill in the gaps in my memory sufficiently to make Lewitt's narrative intricacies easy going.
Finally, the ponderousness of Dancing Vac doesn't exactly make it edge-of-your-seat military SF either; fans of that sub-genre would do better with the likes of David Weber. Lewitt wrote several more novels under the sorta-pseudonym "S. N.", then began writing under her real name again towards the end of the '90's. I imagine she now has many better tales to offer than this awkward non-starter of a duology.