Below are some nice quotes written by Victor Hugo in his didactic novel Les Miserables, which explores many problems in 19th century French society, including social injustice. If you want to know the story, but don't want to read over a thousand pages, you can try to watch its movie or musical adaptation.

On inequality:

As there is always more misery at the lower end than humanity at the top, everything was given away before it was received, like water on parched soil.

If they were richer, we should say they are dandies; if they were poorer, we should say they are tramps. They are simply idlers.

On class conflict:

When they saw him making money, they said "He is a merchant." When they saw the way in which he scattered his money, they said, "He is ambitious. "When they saw him refuse honors, they said, "He is an adventurer."When they saw him repel the advances of the fashionable, they said, "He is a brute."