Space Visitor — Mack Reynolds

It is sometime in the near future.... The nations of Earth have drawn closer together -- there is even hope that a new era of co-operation and progress will soon begin.

These dreams of lasting peace are shattered by one momentous discovery. One of the members of an international team of scientists stationed on the moon has found an alien spacecraft -- with all its incredible technology and weaponry intact. The discovery shatters the illusion of peace on Earth, as each nation joins the mad scramble to learn the terrible secrets entombed by alien visitors eons before.

Only one thing prevents total war -- Werner Brecht, the discoverer of the vehicle, is the only one who knows its location ...and he has disappeared into thin air....