Three quarters of the way through the second of these novels, I thought I'd left the book on the train. My concern at losing a review copy was mingled with my relief that I might not have to finish reading the thing.

The Celestial Empire originated in Roberson's "O One," winner of the 2004 Sidewise Award for Best Alternate History Short Form. It's a neat idea: the 15th-century Chinese Treasure Fleet, reputed to have ranged over the Pacific, has its mission extended as a new emperor continues the outward-looking policies of his predecessor. As the afterwords say, "[b]efore Christopher Columbus sets out to discover a new route to the east, dragon boats of the Treasure Fleet round the tip of Africa and arrive in Europe." The great Christian powers never arise, stifled by the power and reach of the Middle Kingdom. Even so, there is European colonisation of North America from the East, whilst a Muslim Middle Kingdom colony develops in the west of the continent. South and Central America are left to their own devices long enough for a Mexica culture to dominate the isthmus and, after throwing off the yoke of the Middle Kingdom, remain as the only people independent of control by the Manchu emperors. More than a century of cold war follows, with both Mexica and the Middle Kingdom engaging in space exploration, culminating in a Second Mexic War, this time for control of Fire Star, the fourth planet from the sun.

This is fabulous, wide-screen stuff, a setting where any story can be told—and yet, we get World War Two on Mars for two whole novels. Of course, science fiction has spent much of the decades since 1940 fighting and refighting the second world war, on every planet in our Solar System and across the rest of the galaxy or universe, if not over the same streets and fields as those movies still recycled on tired TV. But a plot summary for The Dragon's Nine Sons should suggest why I spent much of the book visualising Telly Savalas chewing on a cigar.

Nine disgraced soldiers, sailors, and marines are given a choice of being executed or accepting a suicide mission to destroy a secret enemy base. Rogues and killers, each of them has a justification for what he has done—a justification neatly provided in an appropriate homily chapter. The group travels in a captured Mexica spaceship to their meeting with destiny. There, they discover that the Mexica have Chinese prisoners, civilians destined to be human sacrifices, and decide they need to effect a rescue as well as destroying the base. They do. Most of the assault team die. The end.

The writing compounds the feeling of a schoolyard retelling of old war movies:

When they had been suiting up and arming themselves in the common area, the men had carried out little rituals, preparing to go into battle. Some had muttered prayers, or tried to strike bargains with whatever supernatural agencies might be listening in. Others invoked good fortune by rubbing good luck charms, as when Ang fondled a small coin he wore on a necklace. Others remembered loved ones distant or lost, as Bannerman Dea did when he took out the lithograph of his lost love, her name on his lips like a prayer, "Lei Xiaoli." Even Yao seemed to go through certain rites, checking and rechecking the action of his knife in its sheath, his pistol in its holster. (p. 270, The Dragon's Nine Sons)

This reads, to me, like a camera ranging across the scene and the writer trying to catch and record what he is seeing. It is distanced from the events, as if the author isn't sure who might have muttered prayers, or who, beyond Ang, may have had a good luck charm. Worse, for an action-driven story, there's no urgency—the story has already moved on and we are stepping backwards to explain how it got here. Both books are dominated by the passive voice, which surrounds the action in cotton wool when the story needs gun cotton. I repeatedly wanted to take a red pen to it: "When they had been ... the men had carried out little rituals"—rewrite! "As the men suited up and armed themselves in the common area, they carried out little rituals."

There are three further tics in these novels that jolted me out of the story: double negatives, awkward caveats, and endless repetition. A couple of examples to demonstrate:

"They might have poor grooming and even poorer personal habits, but it couldn't be said that the Falcon's Claws didn't have impeccable weapons discipline." (p. 152, Three Unbroken)

"The burn off had pushed them slightly off course, but not so far that it couldn't be addressed by a minor correction once they began to decelerate." (p. 265, The Dragon's Nine Sons)

These neatly combine double negative with caveat. Roberson repeatedly sets up strong statements then undercuts them with a "but" or an "although." This occasionally leads to bizarre touches. As Yao thinks back on a pilot who he had never heard of before the current mission, he comes to the conclusion that, "Ang had been a reprobate, a cheat, a thief, but Zhuan had been right about one thing at least: Ang was the finest pilot Yao had even seen, though his skills had been hardly taxed in the course of their mission" (p. 404, The Dragon's Nine Sons). In which case, why does Yao think so highly of the man's piloting skills?

Some of the repetition within the books is a justifiable result of the short chapters, which chop between perspectives, but they do seem to suggest a lack of faith in the involvement of the reader. For example, a key event at the start of Three Unbroken is a decision made by Amonkar Arati, a Hindu, to "become a Murli, devadasi to Khandoba, the divine sword father, Siva incarnate and the guardian of the country" (p. 16). This is a beautiful piece of writing, unpacking a whole culture in the middle of a paragraph about a young woman choosing to join the airforce. Towards the end of the book we get the following: "having decided to enlist with the Interplanetary Fleet Air Corp, Amonkar had pledged herself to the emperor's service, and fancied that she was the bride of the sword father, a devadasi to Khandoba, Siva incarnate and guardian of the country" (p. 360). This is bald repetition that seems to assume that the reader has been asleep at the page. Both books are littered with plot summaries, and the number of times we get "red planet" and "Fire Star" written close together in both books suggests we simply can't be trusted to remember we are on Mars and that the planet is called Fire Star.

One thing Roberson does do well is to make his books naturally inhabit a universe in which the Middle Kingdom is dominant, something which is obvious from the fact that the Han are left undescribed. We hear about the accents of the Chosonese, the height of Britons, the colour of Athabascans. The Middle Kingdom way of life is seen as obviously correct, so that a farm boy from Tejas (on the border with the Mexica, of course) is desperate to pass the bureaucratic exams, as "those lucky few who passed the jinshi-level exams would journey to the Middle Kingdom itself, to Northern Capital, seat of imperial power" (p. 18, Three Unbroken). Indeed "Northern Capital" and "Middle Kingdom" are used throughout—there is no "Peking" or "Beijing," no "China" in these books. The books are written wholly from the Celestial Empire perspective, so there is no need to explain the natural character of the dominant culture. It is possible that Roberson's choice of style, too, is intended to reflect that of Chinese literature, with which I am not familiar. If so, I'm afraid that I am dishonouring his writing masters as I attempt to honour my own.

The Mexica, as the enemy, are repeatedly and actively denigrated. Their technological machinery requires human sacrifice to work. It initially struck me as bizarre that a military spaceship crewed by less than a dozen would need to carry passengers for ritual sacrifice, that even small patrol vessels include an altar with haemoglobin sensors. However, I was gradually convinced that this society is an extreme theocracy, and that such mechanisms could be built into the communications hub of a colony or the central power systems of a space station. Given the primacy of human sacrifice, I can see how blood could stain all important technology. We get a little insight into the workings of Mexica as Our Heroes infiltrate a military station in The Dragon's Nine Sons. Boys are simply warriors who have not yet been blooded, whilst the only women present are courtesans—not "civilian women" (p. 302, The Dragon's Nine Sons). Mostly, though, they are simply the enemy, not particularly honourable even when doubtless brave, and collectively, clearly in the thrall of an evil empire. If the business of human sacrifice did not make this clear enough, we even have, near the end of Three Unbroken, a scene straight out of Auschwitz.

I have said little about the plots of Three Unbroken, perhaps because the three strands at least provide relief from each other. There is a bomber crew, mostly women, although their story is still familiar from any tale of American bomber crews flying hostile German skies in the 1940s; a GI type plodding about the landscape to give us a worm's-eye view; and a special-forces sort, learning important lessons about war and honour and the importance of character over form. This last is a passable tale, marred more by the writing than an overreliance on old movies to generate the plot.

I have quite enjoyed the ideas Chris Roberson has presented in the short stories set in his Celestial Empire in recent years—and had genuinely looked forward to reading these books, with the expectation that he had aligned those ideas with a few hundred pages of story. This time around I have been disappointed, but I still hope that he can do it.

Duncan Lawie grew up in Australia and lives on the Kent coast. His work also appears in The Zone.