I wouldn't say most people buy them, but Ulysses and Finnegans Wake. For me, they're unreadable. Or, I should say I actually read them during a time when I was reading classics that everyone seemed to claim were great, but I didn't know anyone who had actually read them. At the time I was doing it just to be able to say I did. A dumb reason.
I got nothing thoughtful out of either of them. There were some individual sentences and paragraphs that were fun to read just because of the alliteration and poetic flow, but they made no sense. A book written for others to read shouldn't need external commentaries or a knowledge of the author's life and mental state to understand.
Now if someone says they've read Joyce and not for a literature degree, I lose a bit of respect for them, as I did for myself, and as other people should for me. 0/10, not worth, would not buy again, would not read again