The Dark Between the Stars. The Saga of Seven Suns, #9

"A space opera to rival the best the field has ever seen."-Science Fiction Chronicle Beginning a new trilogy set in Kevin J. Anderson's beloved Seven Suns universe, and a horrific new danger threatens the entire Spiral Arm. Two decades after the end of the horrific Hydrogue War, a group of independent gypsy clans, the Roamers, operate giant floating skymines in the clouds of gas-giant planets, where they harvest stardrive fuel at great risk, and great profit.
On the planet Theroc, capital of the vast Confederation, humans live inside a gigantic worldforest whose towering trees are all interconnected in a single mind, which telepathic "green priests" can use for interstellar communication. The stagnant alien Ildiran Empire once ruled the entire Spiral Arm, but they are unprepared for human politics and ambitions. Upon this galactic canvas, a large expeditionary ship goes off to explore farther than any human or Ildiran has ever ventured.
Beyond the edge of the Spiral Arm, they encounter a mysterious and ominous dark nebula, a huge black cloud so opaque that even starlight cannot penetrate it. The explorers are horrified when the dark nebula begins to expand exponentially. The races of the Spiral Arm will be faced with an evil so ancient that knowledge of its very existence has been obliterated, but it will threaten all life, all planets, and even the fabric of the universe itself. HUGO AWARD NOMINEE