They were invaluable in the times before the Internet. I didn't know it back when I was using them, but the Encyclopedia was a French Enlightenment "institution" started by Diderot.
There was also a French classics collection made up of thick, white books with golden letters on the covers.
While the French culture and France herself are amazing and I had a great time traveling there, the truth is, I had learned this language before discovering France by virtue of my mother's influence. I have long associated the French language with aristocratic distinction (despite Liberté, égalité, fraternité) and before being replaced by English, this language used to be lingua franca; one distinction that still holds is that whereas the latter is considered by many, indubitably, the international language of business, French may still be thought of as the language of diplomacy.
(This is a Language I study.)