Maximum warp. Book 2 - Dave Galanter

Starbse 27 has gone dark, functions grinding to a halt as its energy source mysteriously fails. A province on Bajor reverts to pre-cardassian power plants - where it can. Three Vulcan cargo ships are lost with all hands aboard. The mysterious dead zones continue their expansion, creating havoc throughout civilised space. Communication, transportation, medical facilities, replicators - without this technological infrastructure, the United Federation of Planets will descend into primitive chaos.
On board the Starship Enterprise is the one man who may be able to halt the deadly decay. T Sart, an egomaniacal war criminal whom Picard and his crew suspect of treachery and lunacy, plans to save both the universe and his own career by manoeuvering Picard into a position of weakness even as the two men work together as allies. He leads Picard to a planet on the edge of a black hole from which the decay appears to emanate. There, Picard and the Enterprise must hijack technology beyond their comprehension to save the lives of billions - and prepare themselves to sacrifice millions on the planet below.