Alastair Mayer's T-Space Novels

T-Space - terraformed space - 50 light-years across with planets that were terraformed 65 million years ago. The only signs of intelligent aliens - aside from the terraformed planets themselves - are a few relatively primitive species who descended from terrestrial life transplanted by the mysterious Terraformers.

Or at least, that's the theory. The further out humans get, the weirder the things they find, including oddly familiar structures that no primitive civilization could have built...along with hints that the builders, or some other spacefaring species, are still around. But not necessarily friendly.

Furthermore, humans being humans, they're not all necessarily friendly with each other, either.

Current and upcoming titles in print/ebook.

Early T-Space: The Alpha Centauri Trilogy
The trilogy the first expedition to another star, the surprising findings, and the troubles they run into.
Vol. 1: First Landing 9781539132295		Vol. 2: Sawyer's World 9781546913283		Vol. 3: The Return 9781974035489
Expanding T-Space: The Kakuloa Series
This series picks up right after the Alpha Centauri trilogy leaves off, following the ups and downs of settlement of the Alpha Centauri system and exploration beyond.
Vol. 1: A Rising Tide 9781948188074		Vol. 2: The Downhill Slide 9781948188166		Vol. 3: Crash and Burn
Vol. 4: The Tide Turns
T-Space: The Carson & Roberts Archeological Adventures
Starting fifty years after First Landing and building on the Analog story "Stone Age", this series has been described as "Indiana Jones in space". The team is chasing down clues to a recent spacefaring civilization, when they find themselves embroiled in intrigue involving multiple political factions ... and aliens.
The Chara Talisman 978061556238		The Reticuli Deception 9780615711027		The Eridani Convergence 9781948188135
The Centauri Surprise 9781948188180		The Pavonis Insurgence