Les Misérables

An emotionally turbulent story, and a force of moral philosophical ideas. Hugo's writing in this book shows why he is not just among the 19th century's greatest writers but one of its greatest minds over all.
I may not agree with all of his philosophies, but I commend him for how eloquently he addresses the big questions. What does it mean to be a good person? What is it to be miserable, and how can we find joy in a world so full of misery? All this is addressed completely all while telling a heart-wrenching tale.
And if you think you know the story because you watched the musical or the movie, no. You don't. Some of the most central characters in the book get maybe a line or two if that in the movie, and the way all the characters intermingle is genius.

All that said, I would highly recommend reading a quality abridgement. You can cut out massive chunks of this book without any loss of quality to the story or even the philosophies within this book. For example, there are about 8 chapters about the history of Paris' sewage system, and 5 chapters about why it's ok to write in slang. If you skip over those entirely, you would lose nothing.

I highly recommend this to anyone with an interest in the history of France or an interest in moral philosophy. For just the touching story though, abridge.