The irony of the present moment
By creating a story with a scope of over 700 years, London draws attention to his prose as historical artifact. The effect is that his story is regarded objectively, shown as one small part of the vast stretch of time and history. This is an ironic depiction of the present moment, since it goes against our basic assumption that the present moment is eternal. London reminds us that it is not eternal at all.
The irony of espionage and tyranny
The basic irony of espionage is that suddenly, the strangers in the book are not regarded as citizens and friends, but as potential threats. It sets up a paranoia that never really goes away. The second irony attached to this is that the government would need to keep such a close eye on the public. Therefore, it's not a far leap from espionage to full-fledged tyranny.
The irony of capitalism
The irony of capitalism is that in capitalistic systems, there tends to be a large gap between the wealthy and the average, since capitalism rewards success exponentially. This means that the natural decay toward tyranny for capitalist systems is through oligarchy, when suddenly the wealthy and powerful realize that by conspiring and combining their resources, they have more power than the actual government. Another sad irony is that this would have been done behind closed doors, silently, which means that it could have already happened.
That's another aspect of London's argument, since he puts the old story in his own past, since the story is set a few decades before the story was published. It's like he's saying, "How do you know this hasn't already happened? Do you know for sure that the government isn't being controlled by an oligarchy?"
The irony of the future
This novel features an interesting reversal of our commonly understood associations with the future. Instead of making the future terrifying, he chooses to make the future terrifying, and for some reason, this strategy is really effective in creating an unsettling, horrifying tone.
The irony of the paranoia and the last sentence
The tone of the book is largely paranoid. People are worried that someone near them is a spy for the government. People don't know what the government could really do to them if they ended up getting caught. It's absolute terror, and it doesn't ever go away. When the book ends mid-sentence, there's only one real possibility. The writer was caught after all. The paranoia was not for nothing.
