Hunger by Knut Hamsun (1890)

This bleak but compelling psychological portrait of a slightly unhinged and destitute young man struggling to establish himself as a writer while slowly starving has been called the novel from which all twentieth century literature sprang. It's a big claim but I prefer to see this work as part of a natural progression from Dostoevsky through to modernism. That's not to diminish Hunger in any way. Set on the streets of Oslo, this tale of a fellow full of frenzied, self-defeating idealism is said to be semi-autobiographical. Toward the end of his life Hamsun sympathised with fascism, something that has scarred his subsequent reputation.