Moby Dick

At times Moby Dick reads as a history of all things whaling. There are long descriptions of the different types of whales, the accuracy of whale's portrayal in art, the common procedures of whaling vessels and more. (He was convincing in saying that the whale should be considered a fish, even though it has lungs. This goes against are modern way of classifying, but is not made in ignorance, so much as a "sea-centric" means of grouping.
In addition to history, the novel explores human relations. Whaling was a true multi-cultural affair, long before "multi-cultural" was a thing. The novel begins with the narrator sharing lodging with a "cannibal", and goes to describe encounters with many others of diverse backgrounds. While the narrator is initially afraid of these different characters, he gradually treats them as respected crew members (though not necessarily as close friends.)
Even when the book gets into the "action sequences" as they are hunting wales, the author takes time to go into exquisite detail of how they process the whale onboard the ship and the intricacies of the "law of the sea" for who gets to complete a capture of whale.
It is not until the final few chapters of the novel that the focus is truly on being a novel. Now the ship and crew is enduring a typhoon and trying valiantly to battle Moby Dick. Ahab truly will stop at nothing (including his own demise) to help defeat the great whale Moby Dick. The action is intense. You could make a good abridgement by taken bits and pieces of the first 100 chapters and including the last few in their entirety.