I meant that in the most positive way possible. It's a pain in the ass that you enjoy working through (if you enjoy modernist fiction).
It's a really difficult novel, very unkind to the reader, and features Joyce's signature experimental prose - so you have very poetic passages, neologisms, portmanteaus, and segments without punctuation. The most famous is probably the Penelope section, which is Molly Bloom's chapter. Here's a sampling:
None of the other chapters are quite this difficult to parse, but Joyce plops you into various scenarios that make it difficult to follow along, sometimes. If you're really interested in reading and want to put in a little extra work, there's a helpful text called The Bloomsday Book, by Harry Blamires. It's basically a reader's guide to the novel, and very helpful.