Curious, as French rules are mixed for books. A capital is required at the beginning, but another capital is only required if the next word carries equal weight. like "Crime et Chatîment". or like "La Belle et la Bête." Whereas, "Les Fleurs du mal" isn't. Also "Les Misérables" carries a capital as the article isn't counted as the first word.

In fact, works of art carry the same rule. Degas's "Dans un café." which is also called "L’Absinthe"