Future Shock. Future Shock, #1

A thousand years in the future, human civilisation has been driven to the brink of extinction by the Killers, a mysterious alien race seemingly intent on exterminating every other form of sentient life. Desperately fleeing utter annihilation, a handful of starships use an experimental stardrive in a bid to escape, only to find themselves thrown back in time to the dawn of the First Interstellar War in 2308, where mankind is making its first stand against an alien foe.
And they are not alone. For the time travellers, it is a chance to rewrite history, to end the war quickly with futuristic technology, speed up the development of a post-scarcity society and prepare the human race for the second inevitable encounter with genocidal aliens. For the contemporary humans, their mere arrival is devastating; future technology threatens to undermine their society, future historical records name heroes and villains alike before they make their mark, future attitudes and values challenge everything they hold dear. With two alien enemies breathing down their necks, and the fate of humanity itself in the balance, both sides have to cooperate.
But as the impact of the sudden change in history spreads, and time itself is changed beyond all recognition, the threat to humanity may come from human nature itself .