Liberty Gun by Martin Sketchley, is a goodies vs. baddies shoot-em-up, set in the year 2379 on the planet of Serriat. It was a pleasant place once, before the evil Sinz race occupied it.
Human Alexander Delgado, having mated years ago with a Serriat female, and fathered two hybrid children by her, has travelled back in time to the birth of his twin sons. He hopes to stop a string of events that will result in one of them murdering the other.
Time travel, however, has its complications. The operator of his time portal can’t quite land him at the right time and place. Delgado, along with a female human, Ashala, or Ash for short, ends up part of the Serriat resistance.
Delgado, Ash and most of the other characters are occupied by ‘nobics’; intelligent computer programs-cum-parasites. Nobics can judge developing circumstances, and influence the minds and actions of their hosts to keep themselves alive.
What follows is a tale of guerrilla warfare, heroics, interspecies mating,  betrayal, and living spaceships that make agreements with each other to ignore their pilot’s instructions. Delgado discovers that while he can help the Serriats reclaim their planet, changing his sons’ destiny is a whole lot trickier.
The early parts of the book involve a lot of ‘telling, not showing.’ There are a lot of minor characters with fancy titles and limited roles, and plenty of fairly irritating smart-aleck exchanges between Delagardo and Ash. Ash often seems to be a token female, and speaks like a twentieth-century American teenage girl with an attitude problem. For me, this was the one major irritation in the book. This is the third  book of a trilogy, and I hadn’t had the benefit of reading the earlier two, The Affinity Trap and The Destiny Mask. If I had, I would have known that Ash and  Delgado had been lovers in a previous book. Perhaps that’s why I was left wondering why she is even in the book until the very end, when she makes a hard-nosed decision to do something that  Delgado knows has to be done, but can’t face doing himself.   
The plot is well constructed, the pace is fast, and if you like futuristic action with a lot of interspecies cultural and sexual exchanges, you’ll like this.