The Helverti Invasion

After a global war crippled Earth's civilization, lizard-like aliens had assumed they would have no trouble moving in and taking over. Fortunately, secret galactic agents had trained the mystic warriors of Earth, and the invaders had been driven off. But now the Helverti, furry but definitely not cute aliens, are planning to succeed where the lizards failed. Once again it's mystic warriors versus alien technology--and the Earthlings are not weak as they appear.