Omega

This book is the sequel to Chindi by Jack McDevitt, part of the Academy Series which began with The Engines of God. Omega was the Campbell Award winner for 2004. I've enjoyed The Engines of God, Chindi and Omega and look forward to reading the others. These books are right down my alley -readable space opera with 3-dimensional characters, believable women, plots that have some body to them and keep my interest high....

from the back of the book:

For a quarter of a century, humanity has watched as the malignant omega clouds have destroyed every civilization they have come across. Now, it's Earth's turn--but not for another nine hundred years. A cloud has switched direction, heading straight for a previously unexplored planetary system--and its living pre-technological alien society. Suddenly, the need to find a method for the omegas' destruction becomes urgent, as a handful of brave humans, scientists and military alike, try to save an entire world--without revealing their existence...