Importance of victor hugo(not his poems)

He was author of one of the most important novels in France: Les Misérables, may be is the most famous literature French work.
Even the novel have been adapted several times in Hollywood films, and there's a Broadway musical representation that also was adapted in film and was casted by Anne Hathaway in the role of Fantine, and Hugh Jackman in the role of Jean Valjean.
When the novel was released Victor Hugo was already famous, and people was impatient for the novel (kind of J. K. Rowling nowadays), and was an immediate success.
I have never read the book, but is long, it has 5 volumes, each of them it's a book itself.