Here’s a rule of thumb I use in deciding if a book is any good: do I keep putting it down and reading other books instead?
I bought Twenty Thousand Leagues Under The Sea (TTLUTS) in Serbia in November last year. I’d just knobbed a gypsy-looking girl from Nis who had massive  fake tits. I decided that was me done with chasing girls for the year so I wandered into a big bookshop just off the Knez Mihailova main boulevard  to their huge English language section and perused the Wordsworth Classics shelves.
“I’ve never tried Jules Verne. He was the original sci-fi writer wasn’t he?”
I wish I hadn’t. I read thirty pages – this story starts off good – but got distracted with Resident Evil VII and the Mafia III dlcs. I read another twenty pages at the arse end of December and was bored. There were still two hundred pages remaining and I just didn’t much fancy the job. It felt like hard work.
Between starting and finishing TTLUTS I read thirty-seven other books. That’s how poor an impression poor Jules Verne made on me. But what’s so wrong with this book?
Here’s my thoughts.
1. Intention + Obstacle
The key driver behind drama is that the protagonist wants/needs something (intention) and then must try to overcome the obstacles in his way. Think back to any fictional book or movie you enjoyed and you can easily pull out the intentions and obstacles. TTLUTS starts out well with mysterious reports of a sea monster than has rammed ships in every ocean, new stories about it, and then a hunting expedition setting out to kill it. The narrator is a natural scientist aboard the hunting ship. This is the good start the book gets off to:
Intention: Find and kill the sea monster
Obstacle: Locating it, and besting it in battle.
As we all know and the cover makes clear, the “sea monster” is actually the world’s first submarine, The Nautilus, piloted by Captain Nemo. The narrator is rescued from the sinking ship and held politely as prisoner aboard the submarine along with two of his colleagues, his servant Conseil and a grisly Canadian harpooner called Ned Land.
From this point on the intention and obstacle disappears. The rest of the book is just Nemo taking them on an underwater magical mystery tour  and the narrator documenting the fauna and sea life in excruciating detail. There are occasional dramas, such as being attacked by savages, being trapped under ice, but they all come and go quickly. There is no long-term momentum.
This means the book flounders badly. It’s becalmed, like a sailing ship without wind. This more than any other thing is what makes the book drag. It’s aimless.
2. Horrible prose
Jules Verne cannot write a good paragraph to save his life. Some of his paragraphs are so long and turgid that they last longer than an enter page. Each page in this paperback edition has 42 lines and approximately 12 words per line. So, some paragraphs are over FIVE HUNDRED words long. That’s a wall-of-text that would make even the most insane conspiracy theorists of QAnon scholarship think “that dudes’s crazy writing walls of text like that”.
Worse is that so much of the prose is pointless zoological detail. For example:
“The vegetation of this desolate continent seemed to me much restricted. Some lichens of the species unsnea melanoxantha lay upon the black rocks; some microscopic plants, rudimentary diatomas, a kind of cells, placed between two quartz shells; long purple and scarley fucus, supported on little swimming bladders, which the breaking of that waves brought to the shore. These constituted the meagre flora of this region. The shore was strewn with molluscs, little mussels, limpets, smooth bucards in the shape of a heart, and particularly some clios, with oblong membraneous bodies, the head of which was formed of two rounded lobes. I also saw myriads of northern clios, one and a quarter inches long, of which a whale would swallow a whole world at a mouthful; and some charming pteropods, perfect sea butterflies, animating the waters on the skirts of the shore” [page 193]
Did that just paint a memorable image in your mind? Of course it fucking didn’t. That’s only the second half of a paragraph too! Lest you think I chose the worst example, I assure you I just turned to a random page a moment before typing. Imagine page after page of these walls of text while nothing is actually happening in the story. Your eyes will glaze over and you’ll struggled not to skim until there’s some action. 
3. No character development.
Captain Nemo is a well-educated, cultured man who holds a deep bitterness against landlubbers which is never explained nor resolved. Conseil is a polite plucky servant who says “yes sir” and “I should think so sir” to his master. The narrator is fascinated by the sea adventure and wishes to record everything while half-heartedly thinking of escape. Ned Land is a gruff whale hunter who is impatient to get back on land so as to board another boat and start killing sea beasts again. That’s it. The characters are completely one-dimensional. We never find out their back stories, or deeper motivations, or hopes and dreams, or interests. They never change from page one to page 244. Nobody has a character arc and they barely even interact with each other except to exchange pleasantries.
This book is awful. So why is it considered a classic?
I can only assume it was Verne’s imagination capturing the readership. This book was written in 1870 when science fiction didn’t exist. By casting his book as an adventure under the sea and then pretending to document its wonders, the reader could feel like they were getting a travelogue. It reads a bit like a BBC2 Holiday show.
There’s no excuse for the shitty prose or absent plot. It was written a full 25 years after The Count Of Monte Cristo. Frenchmen had long since figured out how to write a good novel.
If you’d like a travelogue of a wild adventure above the sea, gasping in excitement at all the exciting street fauna wandering past the narrator, you’ll have to buy my memoir Balls Deep, A Deplorable Cad, and Adventure Sex
 And I mean massive.
 Belgrade has many bookshops, all of which seem to do a brisk trade. Yet another reason why I like Serbia.
 Living in his yellow submarine. Did you see what I did there?
 Bear in mind this is not scientific witness. Verne is just making all this shit up because half the time the Nautilus is in deep ocean that had never been visited for real.