...of the 20th Century written in English by a Pole! Honestly, you could remove any and all of the prepositional qualifiers from that assertion, and I'd still be willing to defend it. Under Western Eyes is a superb novel in every way - in emotional impact, in intelligence, and in narrative art - and it is very specifically a Russian novel as well as a novel about Russia. Anecdotes suggest that Conrad wrote it in response to his reading of Dostoevsky; if so, he exceeded his model in dazzling narrative acrobatics and in intelligence.
The central character, Razumov, is the most dislikable anti-hero in all fiction, so it's an amazing feat of empathy by which Conrad brings us to care about his fate. Conrad's genius as a narrator is his ability to place himself and the reader in a realm of detachment, so that every event and every character can be observed from several angles at once. The "unreliable narrator" is child's play for Conrad. I don't want to spoil any of the prismatic effect of Conrad's narrative structure by telling any more of the tale of Under Western Eyes, but I will mention that the title is not insignificant.
The Russia portrayed in this novel is a land of cynicism and naivete intertwined - hyper-emotionalism and psychological repression in equal measure - omnicompetent surveillance and hopeless myopia - ruthless bureaucracy and utter disorganization - a land in short of oxymoronic self-destruction. This is NOT, however, the Russia of Communism! The novel was written in 1911! This is Russia as it existed under the Tsarist autocracy, and everything about it clamors for revolution. It's interesting to compare Conrad's portrayal of the old regime with the nostalgic and idealized version served up by Vladimir Nabokov in his memoir "Speak, Memory." Nabokov wrote far more beautiful sentences, but Conrad saw deeper. The horror for us, post-Stalinist readers, in Conrad's depiction of the pre-revolutionary state-of-things is that we KNOW that change will not change much, that autocratic, arbitrary repression will be replaced by...more of the same.
Conrad wrote two novels aground, away from the sea - this one and The Secret Agent. They are among his best. Some readers of today seem to find Conrad's style involuted and dry, and blame it on his status as a 'second-language' writer. To my mind, they are missing the point, the complex lensing of perspective through the minds of Conrad's narrative intermediaries. This is a book to be read slowly and observantly; the effort will be rewarded.