The novel received widespread acclaim and recognition, but also some criticism. Russell Letson's Locus review appreciated the ambitious structure of Leckie's novel, which interweaves several past and present strands of action in a manner reminiscent of Iain M. Banks's Use of Weapons, and its engagement with the tropes of recent space opera as established by Banks, Ursula K. Le Guin, C. J. Cherryh and others. He concluded that "[t]his is not entry-level SF, and its payoff is correspondingly greater because of that."[5]
In the opinion of Genevieve Valentine, writing for NPR, the "assured, gripping and stylish" novel succeeded both on the large and on the small scale, as the tale of an empire and as a character study.[6] Tor.com's Liz Bourke praised Leckie's worldbuilding and her writing as "clear and muscular, with a strong forward impetus, like the best of thriller writing", concluding that Ancillary Justice was "both an immensely fun novel, and a conceptually ambitious one".[7]
Nina Allan's review in Arc was more critical: while she found "nothing lazy, cynical or even particularly commercial-minded" in the novel, she criticized its characterization and considered that its uncritical adoption of space opera tropes and the "disappointingly simple" ideas it conveyed (such as that empires are evil) made Ancillary Justice "an SF novel of the old school: tireless in its recapitulation of genre norms and more or less impenetrable to outsiders".[8]
