It's one of those irresistible ideas we all wish we could have had first: a nun packing six-shooters, roaming the Wild West and righting wrongs, like David Carradine in a wimple.

Over the past year or so, the pseudonymous Stark Holborn has released 12 short books about Sister Thomas Josephine in digital format, and they've remained pretty much under the radar. Now, though, collected into a one-volume omnibus, the Nunslinger saga could catch on in a big way.

Raised in a convent, Sister Thomas Josephine is on a wagon train bound for California which is attacked and ransacked. In short order, she's introduced to First Lieutenant Theodore Carthy, whose men tend to the survivors, and then kidnapped by the outlaw deserter Abraham Muir. Forced together by circumstances, she and Muir become uneasy allies in a perilous journey across the US. And if Muir isn't as bad a man as he seems at first, neither is Carthy as good, and Sister Josephine finds herself caught up in the bitter feud between them.

A homage to dime novels, the Nunslinger series is pure episodic pulp, and Stark Holborn has a seemingly inexhaustible supply of cliffhangers to torment his heroine with. There's no risk of getting bored when you know that you're only a few pages away from the next life-threatening hazard. But what raises Nunslinger above the level of the penny dreadful is the way that Holborn combines this rattling good romp with Sister Josephine's evolving sense of morality.

As befits a woman who grew up in a convent, she regards the people she meets with a compassionate eye, a refusal to judge and the conviction that no one is beyond salvation. Released into the wild and forced into life-or-death circumstances on a regular basis, she has to abandon fixed certainties and be flexible, judging each situation on its own merits without violating her deeper principles. She begins to toughen up quickly, standing up to the handsome but cruel Lieutenant Carthy (who thinks she's bluffing) and is even compelled by her moral compass to break two men out of jail with nothing but her wits, her courage and a loaded gun.

Nunslinger is the Two Mules For Sister Sara that didn't bottle out of its initial premise. And if Quentin Tarantino hadn't already announced that his career as a director is drawing to a close, I imagine that he'd be first in the queue to snap up the rights.