This is a book recommendation, as opposed to a review. I haven't read this book for a number of years, but I cannot forget it, either. That puts it in some pretty select company.
To appreciate it, let's first accept that Aristotelian Physics and Ptolomeic Astronomy accurately describe the universe. So does Chinese Alchemy and Yin-Yang Theory. Within the constraints set by these "scientific theories," the story is a detailed account of the first attempt to enter the Empyrean Circle of the Heavens to capture sunfire. The stimulus of this "big science" project was, naturally, war. The West (under Spartan and Athenian leadership) wanted a superweapon to destroy the cities of the East and bring an end to a millenium-long war with a Chinese Empire, though not the one our world has known. In a way, then, this is a hard science fiction novel, but the science is not what we learn in school.
The book also counts as alternative history. The war between East and West began with Alexander the Great reaching the borders of China and being thrust back. (You are correct. This never happened in our world). The war never ended because it is a clash of civilizations, neither understanding the other. The hero-worshipping, individualistic West could not comprehend the collectivist, bureaucratic East any more than its Aristotelian Physics could accommodate Chinese Alchemy.
There are spies and betrayal complicating the search for the superweapon. There are comments on the ultimate causes of war. There is a very 1960's musing on endless war against an implacable superpower enemy with an incomprehensible ideology. There is a clear analogy to the nuclear standoff in the Cold War. There is also a 1960's-style optimism in the end about individuals forcing nations to change their
homicidal (and suicidal) policies.
Richard Garfinkle published Celestial Matters in 1996, which was probably close to the time I read it. The book is unique, and worth a read. If you don't believe me, then check the comments on Amazon.