John Glasby & J.L. Powers 
Black Abyss [EPUB ebook] 

With the discovery of the hyperdrive, mankind at last possessed the means of going out to the stars. Four expeditions had already gone by the fine the fifth starship left Pluto for Vega. Carrying its complement of scientists and military personnel, they arrived at the solar system of Vega to find one planet sufficiently like Earth to allow them to land. Here, they discovered mystery. The ruins of great cities built on the shattered remains of still earlier fortresses, showing that some great race of conquerors had passed that way sometime in the past thirty thousand years. No life now remained on this planet and speeding to the next sun, they found a civilisation which possessed powers so utterly strange to them that one native almost succeeded in destroying them and taking over the ship. And still the mystery remained, for the legends of the planet spoke of a race of gods who had come down from the stars twenty thousand years before. It was not until they reached the planet of a red giant sun that they ran into a race of creatures so fantastically alien that there was no defence against them, and they learned the real identity of the race which had conquered the stars millennia before…