Please explain Ulysses.
Ulysses is an extremely complex experimental novel in which J. Joyce develops his own version of the stream of consciousness. The story takes place in one single day, and its main theme depicts the feelings of alienation experienced by Leopold Bloom, an Irish Jew, in parallel to those experienced by Stephen Dedalus, whose former history we know from A Portrait of the Artist as a Young Man.
Just as in the Portrait we encountered a son -Stephen- in search of a father, in Ulysses we learn of a father -Bloom- in search of a son. Bloom has lost his only male child at birth, and is haunted by the idea that some kind of reincarnation might bring his son back to him. Short of this, he is willing to metaphorically father Stephen, who is not an orphan, but whose father Simon does not fulfill his role.
Bloom is an ordinary man and a coward to boot, except when, toward the end of the novel, he saves Stephen from a dreadful scrape in which two British soldiers are bent on hurting him. Unlike the mythic Ulysses, Bloom does not ride the seas fighting hideous monsters and avoiding the traps that Poseidon lays for him. What he does is roam the streets of Dublin and struggle against his feelings of inadequacy, always avoiding confrontation and even accepting mockery and disrespect from the "true" Irish. His desperate efforts to be accepted as an equal by his acquaintances turn him into the antithesis of the hero of The Odyssey. The contrast extends to their respective marital relationships. While Ulysses' wife Penelope is an epitome of faithfulness, Bloom's wife Molly is involved in a relationship with her agent. Bloom turns a blind eye to this as well.
Stephen is also alienated from his fellow countrymen because of his foreign last name (Dedalus) and of his hatred of the invaders -the English- only matched by his contempt for the many Irish anglophiles around him and the lukewarm sentiments of the so-called patriots.
Bloom and Stephen cross each other's path many times, but come together very near the end.
On the whole, the novel is written in an amazing combination of styles, with parody and pastiche contributing to some of its most interesting passages.
Please bear in mind that this is just a broad explanation. Full libraries have been written on the subject, and still some aspects of the novel remain open to discussion.