Piers Anthony's Cluster Series Volume 1 - Vicinity Cluster

Description from the back of the book

At the farthest reaches of Milky Way Galaxy, on the planet of Outworld, where primitive men and nubile women still battle giant dinosaurs, the barbaric genius of Flint is summoned by the Earthborn to fulfil a mission of galactic magnitude: to save the galaxy's energy source from the marauders of Andromeda Galaxy by transferring his overpowering Kirlian essence to alien spheres, and uniting the galaxy against the invaders.

Condition - good - there's an old fold on the cover and a slight rip at the bottom left and general signs of age.