Its an entirely self contained system where everyone is performing their role for the machine, which is the society, to operate smoothly. The hierarchy are strictly defined and so is the lifestyle. The horror of living in house made of glass walls isn't as provocative as stripping people of their individuality and basic humane elements. 
 The protagonist, D-503, starts logging his thoughts with utmost vernacular accuracy but he slips from time to time to use a word that's not spoken anymore as they once belonged to the "ancients". Zamyatin gives us a grim dystopian view of a future where only two percent of the entire population exists. The resulting totalitarian "one state" government controls every aspect of humans is considered utopia as the people believe it to be the idealistic way of life. 
 Zamyatin carefully avoids the contradiction of utopia and dystopia but tells the story of a man who finds himself with bunch of emotions that isn't subscribed by the state. He goes to the brink of losing his mind and what follows after is both frustrating and endearingly human. 
 Its the time where dreams are considered to be disease of the mind. With the awakening of emotions, D-503 is deemed to be sick. A fitting end to a world that can no more recognize humanity for what it is. 
 A must re-read every couple of years. As we grow, I am sure the protagonist will offer a different perspective with his frantic ramblings.