The focus of the book is on the travels of Professor Aronnax, his manservant Conseil, and a harpooner named Ned Land- alongside the eccentric Captain Nemo. It's quite the interesting book as far as character dynamics go, as over time Aronnax begins to mimic mannerisms of Nemo over time to a certain degree- this is most notable in how he stops acknowledging arguments that Ned Land has made multiple times, and begins to value word economy(the concept that less words spoken are more powerful words spoken).
Unusually though, the morality of Captain Nemo and the morality of Professor Aronnax are completely at odds. Nemo is an exceptionally misanthropic soul, to the point he will sink ships where he perceives he was wronged in the past. He also attempts to keep his guests from witnessing these atrocities, so he has a perfect recognition that these actions go against the slave morality that the guests follow.
A point on this slave morality-master morality which is an idea taken from Nietzsche, Captain Nemo is a very good demonstration of master morality... up to a point. Aronnax, Land and Conseil all defer to goodness and justice, while Nemo refers to strength, wrongdoing and a wider scale of conflict. Additionally, Nemo also refers quite often to the Christian God- in some ways embracing the role of Jesus when Jesus drove the money changers out of the house of God.
This interpretation can be supported to a certain extent by the library that Nemo possesses, noting the curious lack of books on economic theory- though it is worthwhile noting that while Nemo is almost a complete isolationist, he maintains a network of knowledge and supports revolutionary efforts in material(material that in irony is stolen material that itself was originally stolen via taxes). The lack of books on economic theory is somewhat interesting to me, as economics only bubbles up as a relevant point when dealing with effective distribution of resources in a wider society. The size of the Nautilus does not require such distribution of resources, doubly so given the almost militant rigour of its crew. It could even be argued that it's a militant rigour denoting a cult of personality around Captain Nemo(somewhat possible given the unknown potentially constructed language that Nemo and Crew use, and that when a crewmember was in his death throes he yelled in French, not this odd language).
Another point I found interesting when reading this, is the strange juxtaposition of Ned Land and Captain Nemo, particularly on the topic of hunting. Both enjoy a challenging hunt, but both hunt for different purposes: Ned for sport, and Nemo for food. While Nemo recognises the challenge and rises up to it, he doesn't squander life unnecessarily- referencing how people like Ned Land have driven many different species of animals into near extinction. The way Captain Nemo lectured Land on this, also serves as an interesting point and a sort of catalyst, as hunting is the only catharsis that Ned has aboard the Nautilus- being away from home, away from hunting, away from entertainment, away from alcohol and away from all forms of socialising.
This nature of Ned Land contrasts nicely with the relationship of Professor Aronnax who can talk to Captain Nemo on his observations, his mentoring and discussions with Conseil... and of course the fact those of a scientific persuasion typically have less inclination towards socialising.
Regarding the setting and the technology presented in the book, it is remarkable to me how much it got utterly right. If I was utterly pedantic, I could raise issue with Atlantis, with convenient underground underwater sections and the like, but all of these go forward to raise Captain Nemo's status into a legendary status- as a man who values actions and lets the opulence and tranquillity of his domain speak louder than his words.
On the topic of his domain, I found his expedition to the South Pole to lay claim to it against all the attempts of other nations as a particularly interesting thing, especially as it was timed just at the Southern Equinox, and as it was covered in shadow, almost representing the nature of Nemo's disposition. Following this, he was utterly at the mercy of nature but remained steadfast, resolute and in stoic control of the situation despite the uncontrolled nature of the icy seas when locked beneath the ice caps and running low on oxygen. He remained open to many different solutions too, and changed tact accordingly- more than can be said of most people in this world when facing difficulties.
I will take a moment to discuss on a tangential note, the 1954 Disney Movie, 20,000 Leagues under the sea, as its interpretation of Captain Nemo I found quite interesting. They portray him similarly, but more commandingly- however using creative liberties they chose to focus more on the interactions of Ned and the Captain, and between Aronnax and the Captain- and to present the Captain as a more talkative and revealing person, and honest too. Additionally it puts just a bit more fire into when he is committing acts of terrorism, as he plays Tocatta and Fugue in D Minor, a particularly heavy and melancholic Organ piece of J.S. Bach(also helping present him as a man of good taste) before he commits to his action, which has the effect of catharsis and once again revealing how hatred is a substitute for love, to dominating effects towards monomania. The ending message of the movie lies in stark contrast to the ending message of the book, while in the movie it presents it as hope for the future of humanity, the book presents Nemo as a tortured misanthropic soul, too far gone that there is no saving him, and too tyrannical that they must get away from him for all their minds(maybe not Conseil since his chief concern is the professor, but the professor from mimicry, and Land from homesickness).
Returning back to the book, on other elements regarding the book. One particular element I despised in this book, is the constant tangents of tired classification of fish- to a marine biologist I imagine this would be exciting- I am not a marine biologist, I am a layman, and to me it got tired and uninteresting quickly. It serves two purposes to my mind, to present how the Flemish boy Conseil was also utterly devoured in scientific interest, and to present how the Professor writes the text as a sort of memoir and denoting what classification they do on board the ship, and to distinguish between the various environments.
In a similar note, I got a much better appreciation for the structure and positioning of seas, straits and oceans, as well as a better idea for how navigation is done(especially on the poles where magnetism fails to identify the true pole). One particular aspect that stuck with me was the discussion about the Red Sea, Caspian Sea and Dead Sea, and the Suez connecting the Red Sea to the Mediterranean. Regarding this, I had a poor appreciation of it before this book. It's remarkable how the Captain used logic and luck- observing the presence of the same animals in both environments and deducing an underground connection and verifying this. This seizing of opportunities and deduction by logic is both serendipitous, and referred to as luck and logic but more logic than luck- a stance I can completely agree with on most subjects.
Politically, I think Captain Nemo has an unusual view on things. The text I read presents him as wanting fair distribution of wealth, but I object to this, on the fundamental inequalities in human nature- however what exactly is meant by fair isn't elaborated. On one hand, it could mean and equal distribution, on the other a logical and logistical distribution as drawn up by a quartermaster, on the other hand an irrational and unusual distribution driven by market forces(inherently irrational, and not always well distributed). Towards the world, I think his misanthropy and isolationism is an attitude I agree with, but his approach of revolution is one I disagree with. An approach by accelerationism may have been more effective, or an approach of societal apathy might also be more effectiv - though Nemo's issues are on the oppression of people by an unknown nation(implied to be the oppression of Indians by the British, but seems to be left open so the reader can fit whatever relevant nations they see fault in). His individual misanthropy is fully understandable when one considers how he lost his parents, his wife and his child due to the tortures and evils exacted on him by that same society.
As for the technological accuracy of the book, I can say it got a lot right- but again I am a layman on topics of engineering, physics and marine biology so the preciseness of how right it is could be debated. I found the politics and philosophy of Captain Nemo to be more interesting than this pedantic scientific correctness though.
Overall, an enjoyable read- even if the scientific classification rambles of Jules Verne were boring.