20,000 Leagues Under the Sea was the sixth of Jules Verne’s “extraordinary voyages,” published in the same year as De la terre à la lune (1865; From the Earth to the Moon, 1873). Earlier books in the series visited a strange underworld at “the centre of the earth” and the North Pole, unreached at the time, as well as traversing Africa, Australia, and South America. After 1870, Verne began to give more attention to the plots of his novels, but 20,000 Leagues Under the Sea belongs to a phase when the joys of imaginary tourism were sufficient in themselves to sustain the production of long and languorous hypothetical travelogues.

Although it is rightly regarded as a classic of science fiction, Verne invented far less than modern readers sometimes realize. The American inventor Robert Fulton had tried to interest Napoleon in his submarine boat—also called the Nautilus—in 1800, and Verne had several opportunities to observe submarines being tested in the river Seine. He had certainly seen the model of Charles-Marie Brun’s Le Plongeur that was displayed at the Paris Exhibition of 1867. Verne’s most significant innovations were the powering of the ship by electricity extracted from seawater (a technology that continues to prove elusive) and the diving suits used by Nemo and his crew (which would be fatal to users because of their lack of pressurization).

On the other hand, it is difficult for modern readers to realize how mysterious the undersea world was in Verne’s day. Thanks to underwater photography and television there is now a window into that world, but Verne had none at all. The surface of the moon, which the heroes of From the Earth to the Moon observed at close quarters, was thoroughly mapped, at least on the side facing the Earth, but the world under the sea was entirely hidden, known only by virtue of what was cast ashore or hauled out by fishermen’s nets. Verne’s travelers were venturing into an unknown world for the very first time, laying its wonders bare to an audience that had few of the preconceptions that modern readers cannot help but bring to the text. His research was as conscientious as it could possibly be, given the limitations of the available information, and he did an excellent job of weaving a memorable picture around that research. Pedants may complain that he makes seawater far more transparent than it actually is, but he did so with the best possible motives.

In its early phases, 20,000 Leagues Under the Sea is a mystery story, and the mystery must have been effective in the early days, when readers of the book did not know that the mysterious “sea beast” pursued by the Abraham Lincoln was not a beast at all. To modern readers, the long opening sequence seems like a mere prelude to the real focus of interest, which is the Nautilus and its enigmatic captain. Nemo remains a charismatic figure, a perfect incarnation of escapist dreams. Humans are, of course, gregarious beings who cannot live well in the absence of a surrounding society, but that force of necessity inevitably creates tensions and frustrations that lend considerable power to the fantasy of “getting away from it all” and becoming entirely self-sufficient.

Nemo is a strange man, so full of vague hatreds and contempts that he is much less appealing than Ned Land or Professor Aronnax, but that does not make him any less enviable in his splendid isolation. One cannot share his misanthropy wholeheartedly, but it is precisely because it cannot be shared that one is able to understand it...