Call me Mr. B Grades. Some weeks ago- never mind how long precisely- having little or no money in my wallet, and nothing particular to interest me on my shelf, I thought I would go see about that watery part of literature that people often talk about but nobody has ever seemed to have actually successfully read. For instance, my brother has assayed the task twice and given up.  But I've come across the first chapter in several places previous and have thought that I might be up to the task despite others failures.
And so I set out on my journey. 
The truth is, the story of Moby Dick, Ishmael, Queequeg and Ahab is really rather short. But wait you say, the very version you have linked to is just shy of 600 pages. How can you say it is a short tale!?
Well the book may be ~600 pages, but only about 150 of them are given over to any type of story.  The vast bulk of the book  is nothing short of a primer on whales. Identification and categorization of whales. The biology of wales. How to harpoon and kill them. How to dismember them and then how to get the various and sundry things that one might be inclined to find in whales out of the them. The history of whaling. The relations ship of whalers and whaling ships to other ships and other people. The economics of whaling. And lots and lots of pages about why wales (and the sperm whale in particular) are awesome.
In truth the book should be titled: Herman Melville's Cetology Primer (Now with a free short story entitled Moby Dick!).
So, if you ever wanted to know how to separate a whale from his head or how to peel a whale like and orange, then I highly recommend the book.
If you want a story about whaling. The actual story is pretty good. But you've got to wade through a lot of stuff to find it. In fact, a fair amount of what does make up the "plot" of the book, is merely a device for Melville to move from talking about how to boil whale blubber to talking about how to throw a harpoon.
Also the first 100 pages or so occur before Ishmael even makes it onto the boat. So when you are all said and done the actual story can pretty much be summed up like this: 
A bunch of whalers set out to kill whales.
The captain is nuts and wants revenge on a whale that bit off his leg.
They sail all around the world looking.
They find the whale and it kills everyone except the narrator.
There you go. And I didn't really leave much out at all.
Oh yeah, and Moby Dick himself is only in about 10 pages tops. 
Moby Dick: B-
Herman Melville's Cetology Primer: A-
 - And it seems to me that is twice more than 99.9% of the rest of the population.
 - Of reading the book. The journey to get the book was a simple one of walking to the bookshelf in the garage.
 - And I'm probably being generous by saying 150.
 - And boy is it bulky.
 - Warning huge spoiler ahead! Not that you're going to read the thing anyway.
 - And it's the last ten pages.
P.S. - You can get the book on Kindle for free.