This is book 3 of a 3 part series. They are well worth reading if you like realistic stories and science. No fantasy here.
The U.S. Space Marines are called on again, this time on Saturn's moon. Something is alive under the ice and the Chinese will stop at nothing to get there first. Another fine military space opera by Douglas.
Really good space opera!
From back cover:
2040: Ruins of ancient civilization uncovered on Mars reveal startling truths about the creation of humankind.
2042: In the gray dust of the Earth's Moon, an extinct enslaving race left behind more answers, more questions...and a grim warning.
2067: As Earth's warring factions clash in space for scraps of alien technology, a strange artifact lies trapped beneath the ice-locked oceans of Europa: a machine that holds the key to the final human destiny.
It is called "The Singer" for the eerie tone it emits. An artificial intelligence built eons ago, it may ultimately solve the mystery of the vanished alien races responsible for the birth and development of humanity. But after decades of war, the hostile nations of Earth care more for power than for knowledge. And now all that stands between the coveted Al and an all-out Chinese assault is a vastly outnumbered contingent of U.S. marines, dug in beneath the baleful red eye of Jupiter. As terrifying events light years distant begin to converge---with confrontation imminent and annihilation inevitable---a secret history of creation and doom must at long last be contended with...if humankind is to finally claim its glorious heritage among the stars.