What makes Portrait of the Artist as a Young Man a modern novel?

When Ulysses was published in Paris in 1922, many immediately hailed the work as genius. With his inventive narrative style and engagement with multiple philosophical themes, Joyce had established himself as a leading Modernist....Ulysses examines the relationship between the modern man and his myth and history, focusing on contemporary questions of Irish political and cultural independence, the effects of organized religion on the soul, and the cultural and moral decay produced economic development and heightened urbanization. Many scholars mark the beginning of the modernist literary movement with the publication of James Joyce's 1922 novel Ulysses. Joyce's strategies for depicting the events in the life of his fictional protagonist, Leopold Bloom, have come to epitomize modernism's artistic assault on modes of more conventional fiction.

Wikipedia actually has a great entry for modernism, what it means, and the ways in which Joyce and other authors defined the movement. There are also quite a few sites on Joyce that are fantastic, but they all seem to analyze the texts rather than really look at the movement itself. I don't think that's what you are looking for.

Gradesaver also has a great biography of Joyce and information about his works.

The modernists were writers who changed from the "typical" way of writing that had come before them. They often wrote novels in the first person, and they fragmented them, sometimes rearranging the order of the events (i.e., they veered from the typical beginning, middle, end arrangement). Joyce was especially fond of the "stream of consciousness" style in which the narrator gives the reader a view of the inside of his/her mind. Like other writers of his time (and indeed some consider his writing to be the beginning of such writing), Joyce tried to show how to bring some order out of the anarchy that ws typical of the world post-World War I.

I DONT KNOW THE ANSWER COULD YOU PLEASE HELP ME