This is one of the most fascinating books that I know of. I'm pretty well convinced that the world population of people who have read more than the very beginning and very end probably numbers roughly the count of my fingers and toes combined. Although I think many people
I also think the the only person who ever really understood the book was James Joyce himself. Fluency in multiple languages down to idiomatic expressions and deep etymology seem like strict requirements if you have never occupied the meatspace between Joyce's ears.
Any small portion seems somewhat comprehensible in its highly local environment, and a bit funny or witty in how it's written. But then it breaks down when attempting to connect that piece to the wider whole. And it all makes me feel like I'm reading extremely familiar words whose meaning I can't quite remember.
In refreshing my memory about it before commenting here it made me laugh to see that even the best Wikipedia can say about what goes on in the book is that readers have mostly reach a consensus (but only a consensus!) about normally trivial matter of fact such as the cast of characters, a little less so the plot, but that many other important details amount to poorly mapped terrain.
And because I was born with the usual amount of fingers andntoes, if I met a random person in passing, and they claimed to have read the book completely, I would look at them with as much belief as if they had said "I'm a very powerful leader of one of the G20 nations". Actually I might believe the G20 claim a bit more because I would consider it less likely for someone to make a claim like that when it could so easily be proven false if it was not true.
If I had not encountered the book long ago then I might believe it to be the output of an extremely oddly trained gpt-3 model. I don't mean that to be an insult to the book, it's just the best comparison I can think of to characterize it's contents in modern terms.
This is how fascinating Finnegan's Wake is as a literary work.