For the record, Ulysses is at least a full order of magnitude more comprehensible than Joyce's next book, Finnegans' Wake.
I'd also expect it to give a skewed response on a test of this kind because it is composed of a number of different sections, which vary considerably in their style. But maybe that's the point of including it.
Here are Finnegans Wake graphs. It is indeed even more complicated. https://github.com/vocapouch/vocapouch-research/blob/master/....
Number of Pages: 729 Number of Total Words: 218793 Number of Unique Words: 50872 You will know 90% of words after 387 pages which are 53.09% of the book. At that page, you will know 60.64% of unique words.
I'd also expect it to give a skewed response on a test of this kind because it is composed of a number of different sections, which vary considerably in their style. But maybe that's the point of including it.