Empire From The Ashes
This is an omnibus edition of three early novels by David Weber: Mutineer's Moon, The Armageddon Inheritance, and Heirs of Empire. This story is grand scale space opera, and it's a great deal of fun.
In Mutineer's Moon, we find that Earth's moon is actually a disguised starship named Dahak that has been in place for 51,000 years. It is following the orders of its captain, to quarantine a group of crew members who mutinied, fled to Earth, and have used their superior technology to control and reshape the destiny of the human race. Dahak has over the millenia become self-aware and more autonomous than his initial programming allows; he impresses astronaut Colin MacIntyre to be his new captain. There is a new urgency to Dahak's actions. He was part of the fleet of an interstellar empire, the Fourth Imperium, which was formed to combat the repeated encroachment of the genocidal Achuultani, and readings from still active sensors tell him that the Achuultani have returned and are a couple of years away from Earth. War against the mutineers ensues.
The Armageddon Inheritance chronicles the larger war against the Achuultani and the formation of the Fifth Imperium.
Heirs of Empire tells the story of an unbelievably ruthless and deadly conspiracy against the Fifth Imperium by one of the human descendants of the Dahak mutineers.
Despite coming out early in his career, these novels show many of Weber's considerable strengths: tight plotting, furious action, intricate political maneuvering; and few of his faults: straw man characters (his villains especially tend to be rather two dimensional) and bloated prose (he handles exposition by resorting to huge info dumps, often in the middle of conversations).
Weber often has pivotal events happen off-stage and then has other characters tell the reader what happened. This greatly dilutes the impact of the climax of one of the plot strands in Heirs of Empire. A more stringent editor could help keep this from happening.