Giants' Star by James P. Hogan
Paperback. Condition: Good-. 1983. Del Ray. Stock Image. Remainder copy.
Book 3 in the Giants' series. In the 21st century, scientists Victor Hunt and Chris Danchekker, doing research on Ganymede, attract a small band of friendly aliens lost in time, who begin to reveal something of the origin of mankind. Finally, man thought he comprehended his place in the Universe . . . until he learned of the Watchers in the stars!