James Alan Gardner has been telling stories about the interstellar "League of Peoples" for several years, but while the previous books were good, Hunted (Eos, $6.99) is exceptional.

It’s the story of Edward York, an undistinguished Explorer in the human space navy known as the Outward Fleet. York has spent most of the last 20 years on a base orbiting a planet ripped apart by civil war, mourning the death of his twin sister.

He has finally been ordered home, and has been picked up by a ship of the Fleet. Unfortunately, as the starship Willow leaves the system, everybody on board but him dies.

Death to non-sentients!

The cause of death isn’t a mystery -- in fact, it’s one of the fundamental concepts driving the League of Peoples series.

In Gardner’s universe, the galaxy is filled with advanced species, some of which are billions of years ahead of humanity in their development. These superbeings have their own concerns, and aren’t interested in ruling or even interacting with the puny younger races.

The advanced races of the League don’t care what lesser species do as long as they don’t make trouble. They also have a simple definition of "trouble": any being that deliberately kills another sentient being for any reason other than immediate self-defense is by definition "non-sentient."

The League doesn’t allow non-sentients to travel between the stars. Anyone who tries dies the moment he leaves his star system – no pain, no suffering, no exceptions.

That simple rule has several story-inspiring complications built into it -- the League doesn’t care if you’re a traitor or a schemer, so you can do all sorts of horrible things to people that don't involve killing them. There’s no shortage of villainy in the galaxy.

There are firm limits, though, and when Edward York finds himself the only survivor aboard the Willow, he knows that the entire crew of the ship must have committed an unspeakable crime.

Finding out the nature of that crime presents an unusual mystery that leads to many other questions. Gardner is a master of tight plotting, and he’s wrapped the story in layer after layer of secrets and hidden agendas.

A few of the revelations are easy to guess, but they’re red herrings to distract you from the important surprises. The one thing you can count on in the League of Peoples series is that every detail is significant, and will usually come back into the plot from an unexpected angle.

There’s also plenty of action to keep the story moving. Gardner’s pacing has improved in each of his books; Hunted gets rolling with a breathless escape sequence and never slows down.

However, what really sets Hunted off from the previous books is its widening perspective. Gardner introduces us to two new planets, details two unusual alien races -- including a parasitic moss that’s more advanced than humans and isn’t afraid to say so -- and hints at a larger story lurking at the heart of human civilization.

In an era where even small countries can develop devastating nuclear or biological weapons, war and other forms of direct conflict are becoming too dangerous to pursue. Humanity is reaching a point where killing people off is no longer an acceptable solution to its problems.

That’s the question at the heart of the League of Peoples series: what do you do when you can’t solve any of your problems with a phaser set to "kill"?

Fortunately, that’s just the subtext, and Gardner never lets it drag down the adventure. Hunted has some serious thoughts behind it, but it’s so much fun to read that you may never notice them.