It's a bit of a surprise to find Edgar Rice Burroughs conversant with calculation of light years. There's no good reason he shouldn't be, but I've always thought of him as the fantasy end of science fiction, or even science fantasy. The issue isn't too distracting, however, since the rest of the story is ERB pulp through and through, with a strong tinge of WWII.
Written toward the end of Burroughs' life, and doubtless intended as the start of another series, the book consists of two novellas meant for serialization, and with fairly abrupt endings. The plot is thin, and draws on one of his favorite themes - a capable Earth man suddenly transplanted to strange locales, where thinly-clad women admire his genius.
In this case, the country of Unis (representing Good) is at total war with Kapar (which is greedy, rapacious, violent, and fearful). In case you should miss it, Burroughs takes care to point out similarities with Nazi Germany (the book was written in 1940, and presumes war with Germany into 1989). While initially I hoped for a little subtlety and surprise, the Kapars are just as evil as you might expect. I presume it was cathartic to write, and perhaps cathartic for Americans to read, but the story lacks anything approaching subtlety.
Burroughs stretches the capable hero point more than a bit - an ace pilot whose reaction to death is largely 'oh, well', his protagonist is also a designer of experimental engines, and is quite capable of clearly establishing his location as half a million light years from Earth, based on his intimate knowledge of the characteristics of distant galaxies. Very John Carter, in other words.
All that said, the book is a fairly fun read. There's a pretty strong sexist tone throughout (strong women are the ones that don't cry for their fallen men), and more than a hint that blood breeds true, but that's par for the course with Burroughs. If you can set that aside, it's fast-moving and reasonably rousing. Set aside your desire for black and white to have tinges of grey, and it's clear-cut action/adventure.
Burroughs sets each of the two sections off with an unconvincing explanation of ghostly hands typing the story for him. It allows him to start the second with a quick summary of the first, but is otherwise just a distraction.
I can't say that Burroughs became a substantially better writer between Barsoom and Poloda, but certainly the action is clearer. The story has its drawbacks (sexism, lack of realism, blunt wartime references, chopped ending), but it's lively and unexpectedly funny in places, and if you enjoy Burroughs' other work, there's no reason you shouldn't enjoy this as well.