One of the greatest works of English Literature as well as one of its most difficult. Joyce's experimentation with the novel, with the written word, with language, and with the human mind was monumental and defined the Modernist movement and all that has followed.
If you give the time that this lengthy and complex book asks of you it will likely reward you with one of the greatest experiences in reading you have ever had or, possibly, one of the worst. Take the chance.
For a good introduction to Joyce read "James Joyce" by Richard Ellmann. If you liked Ulysses, try Finnegans Wake. If you didn't, try Dubliners.