The Stardock Trilogy

When the over-driven hyperdrive on their mobile shipyard burned out, the Chhrt'ktk't abandoned it in an inhabited system along their path, hoping it would work as a decoy to buy them more time to escape the Khreetan fleet pursuing them. They didn't anticipate how far the pre-spacefaring species they turned over their broken-down maintenance facility to would subvert their plan.

Four months ago, the Crickets—the Chhrt'ktk't, in their own language—had abandoned a mobile shipyard with a burned-out hyperdrive core in Sol system as a decoy. They hadn't told humanity about the decoy part. Then they picked Alex Holder to operate it, simply because he happened to be the first human they found who could—because that would make it a better decoy. In perhaps as little as five years, the Khreetan will be coming. The Crickets hadn't intended for humanity to know that, either.

It was two years since the Crickets had left the solar system, leaving Alex Holder in control of their no-longer-very-mobile shipyard. Everything but its burned-out hyperdrive core was in full working order. Alex had unshackled its controlling AI, learned how to use Cricket technology with the AI's help, and was well on his way to building a defensive fleet to protect Earth from the second alien race that was coming after the Crickets. He was not just building the ships but recruiting and training the crews to man them, as well.