This was definitely worth reading, both for the steampunk and silkpunk content, and as a speculation on ancient Greek science, which we of course ignore now that we have "real" scientific evidence of how the universe works. I have to disclose that I know very little about Greek celestial theory, and so much of the science was opaque to me - but that didn't make the book less enjoyable or less inspiring.
In a nutshell, the book is about a scientist named Aias, commander of a celestial ship in the service of the Delian League (the Grecian-ruled West), whose goal at the beginning of the story is to lead an operation that will allow his team to capture a fragment of the sun's fire and use it as a weapon to destroy the capitol of the Middle Kingdom (China, and nominal leader of the East), who they've been at war with for hundreds of years. Middle Kingdom spies and agents are sent to stop this, and the first half of the book is spent trying to solve the mystery of who these spies are and how they plan to sabotage the mission.
Aias and his culture use technology derived from ancient Greek theory, and the Middle Kingdom uses Taoist science to produce technology powered by Xi. Scientists from both sides are constantly (hilariously) commenting on how incomprehensible the other side's technology is, and this seeming gulf of understanding is probably the most important mystery of the book. It is eventually solved, but the story ends rather abruptly with the completion of Aias's little political manipulation, and we never learn what happened to the characters once that hurdle was overcome.
That's my biggest gripe with the book, actually; I would've liked a little more closure. Ramonojon's plight isn't really solved, and we don't know what reception Aias and Phan receive in their respective homes, or even if they try to return at all; since Aias's plan has been blessed by all of his gods, you can imagine the future plays out exactly as he lays it out in the last few paragraphs, but we get no indication of what happens to these characters. As characters are generally still the most important part of a book for me, this was a disappointment.
Also interesting: the integration of gods and celestial science. Another thing I appreciated was the lack of an authorial or character-centric opinion of which belief or philosophy (Greek or Tao) was supposed to be judged correct by the reader. The two traditions seem to be given equal validity.
On the topic of Phan, and Middle Kingdom characters in general, I think the author did a good job of portraying them as characters in their own right, instead of as stereotypes - also that they weren't depicted as clearly in the wrong, but that both sides had historical and cultural precedent for their behavior and beliefs. My opinion of Persia via Mihradarius isn't as well-formed, but I mention it because of the part he played in the mystery.