WTF is the language and diction of this James Joyce book Finnegans Wake?

Last week, I read that James Joyce is one of the best novelists of all time, so I went to the library yesterday to get one of his books and I picked out Finnegans Wake.
It's 628 pages long and without exaggerating one iota, every single seperate lone sole individual sentence is pure gibberish and incoherent. I gave up after less than a page (and it took me two or three tries to make it as far as I did). They'd lock me up in the funny farm if I read much more. It reminds me of Dr. Sues and this guy they called forgerbot who used to forge my email address and post posts using it with hundreds of words rearranged randomly to deliberately be uninterpretable.What is all of this gobbledygook? Is this the way people in Ireland spoke around the 1890s and early 1900s? If not, then what was his purpose in writing whatever the hell it is? It would drive me batty to read one page even!! I went back to the book about four times, only to flip through it randomely to try to figure out what the deal is and so I kept wondering if it was translated into a foreign language because that's how much it doesn't resemble any English I've ever had to deal with.

It's almost as if it's one giant Guiness-Book-of-World-Records-style poem. Which begs a new question? Is he really one of the best novelists in history and if so, this begs the question How come up until yesteday, I would not have been able to name any of his books (and that most people
couldn't either) and how come they weren't made into movies, and if they were, how come they aren't well known and profitable?

I'm just gonna open the book at any random page and type up the first paragraph I see to post in here in the hopes that someone can explain.

Page 392, the 2nd paragraph (which is continued onto the next page)

And where do you leave Matt Emeritus? The laychief of Abotabishop? And echullard of ffrench and gherman. Achoch! They were all so sorgy for poorboir Matt in his salwater hat, with the Aran crown, or she grew that out of, too big for him, of or Mnepos and his overalls, all falling over in folds sure he hadn't the heart in her to pull them up poor Matt, the old perishgrime matriarch, and a queenly man, (the porple blussing upon them!) sitting there, the sole of the settlement, below ground, for an expiatory rite, in postulation of his cause, (who shall say?) in her beaver bonnet, the king of the Caucuses, a family all to himself, under geasa, Themisletocles, on his multilingual tombstone, like Navellicky
Kamen, and she due to kid my sweatpea time, with her face to the wall in view of the poorhouse, and taking his rust in the oxsight of Iren, under all the auspices, amid the rattle of hailstorms, kalospintheochromatokreening, with her ivyclad hood, and gripping and old pair of curling tongs, belonging to Mrs. Duna O'Cannel, to blow his brains with, till the heights of Newhigherland heard the Bristolhut, with his can of tea and a purse of alfred cakes from Anne Lynch and two cuts of Shackleton's brown loaf and dilisk, waiting for the end to come. Gordon Heighland, when you think of it! The merthe dirther! Ah ho! It was too bad entirely! All devoured by active parlourmen, laudabiliter, of woman squelch
and all on account of the smell of Shakeletin and scratchman and his mouth watering, acid and alkolic; signs on the salt, and so now pass the loaf for Christ sake. Amen. And so. And all.