What's wrong with episodic? The wikipedia entry for the 1954 adaptation of 20,000 Leagues under the Sea quotes a critic as saying a virtue of the film is that it avoids the "episodic" quality of the book. I remember seeing Tim Burton saying he wished to avoid an episodic quality to his Alice in Wonderland to make it superior to other adaptations, perhaps being unaware that the original novel, Alice's Adventures in Wonderland, was very episode, as indicated by the word "Adventures", plural. In both cases, the avoidance of an episodic format narrows the scope of the story and shrinks the impression of large fantasy worlds brilliantly established in the book. However, the 1954 20,000 Leagues under the Sea is not a wholly bad movie.
The novel by Jules Verne evokes a variety of locales through intensely detailed description, has exciting and tense action scenes, and features a great character in Captain Nemo, who comes across very distinctly despite his own reticence. The 1954 film's portrayal of him is in some ways a commentary on the book's portrayal, as much of the movie feels as though the writers were attempting to distil and translate aspects of the book for a 1954 American audience. Professor Aronnax, a captive of Nemo's onboard the Nautilus submarine, confronts Nemo in the movie about his hypocrisy, in simultaneously condemning humanity for its warlike nature and yet violently pursing a lifelong vengeance against an unnamed country. The details are in the book, though they're never tied together into a thesis statement like the one Aronnax gives, but it doesn't need to be because the picture becomes clear in a book that's taking its time, allowing the aspects of character to come through subtly.
But this doesn't mean its one of the movie's bad points--I think it's an accurate enough reading of Nemo and Nemo's played beautifully by James Mason, who at all times, with his every word and action, seems like a man who has an abiding pain which keeps him exiled from humanity. There's a real brilliance in Verne's decision to create a character like this for a story about undersea exploration, the alien and dark tranquillity of the ocean depths beautifully reflecting the shape of Nemo's mind.
Aronnax as the narrator of the book, which is told in first person, is almost completely sidelined in the movie, which doesn't surprise me. The book's focus is more purely on scientific wonder and exploration, which have little place in the film which almost seems to hold contempt for the refined scientific gentleman, favouring a more fight and conquer attitude in the other characters. The many passages of Aronnax bemoaning man's destructive effect on the ocean and the world's ecology is sadly absent in the film.
Also evidently deemed too dated was the master and servant relationship between Aronnax and Conseil, which is a shame since Conseil is played by Peter Lorre in the movie. The movie instead makes him Aronnax's apprentice and a much more independent minded character who is rarely hesitant to contradict the professor. However, one of the nice things about the movie is Lorre's chemistry with Kurt Douglas who plays a more boisterous version of the book's Canadian harpooner Ned Land.
My favourite bit is when the two are playing around in Land's quarters and Land punches Conseil for spying on him. Conseil looks wounded as only Peter Lorre can and says sadly, "I thought we were friends," to which Land laughs and assures him they are and offers to let Conseil punch him in the face in return. Conseil replies with a sock to Land's gut, thrusting his chin forward and that moment one thinks, "Hey, Peter Lorre could maybe beat the shit out of Kirk Douglas. Huh."
The designs of the submarine interiors are beautiful and fascinating and one can see the steampunk movement owes no small debt to the movie for its aesthetic. Which makes it all the more disappointing we don't get to spend as much time with it as we do in the book--there are so many adventures absent--the tunnel from the Red Sea to the Mediterranean, the battle with sperm whales, the journey to the south pole and the Nautilus getting caught inside an iceberg. The battle with a group of giant cuttlefish in the book is changed to a battle with a single giant squid in the movie, which isn't so bad although it involves some of the creative condensing that doesn't work so well in the movie, namely Nemo's relationship with Ned Land. Obviously the people at Disney felt audiences wouldn't accept the fairly laid back and respectful attitude the two have towards each other in the book.
There are other problems with the movie, too, including Nemo's trained pet seal--a distinctly Disney-ish misstep. But it works as a sort of light tribute to the far superior book.