It so happened that I watched the excellent
musical twice before I read the
novel (the latter took more than 8 months: I am a slow reader). While usually there is a lot to criticise in adaptations, in this case I feel that the musical represents the spirit of the book very well. In fact, the genre of the musical may be better suited to the cartoonish plot of Les Miserables than that of a novel. This is not to say that there is nothing interesting among the things that didn't make it into the musical. There is, even among Hugo's ridiculously long asides, but I am not sure there is enough to justify 1500 pages.
Take, for example, the character of Cosette, the female protagonist of the second part of the story, who is the "stepdaughter" of Jean Valjean (the main character) and becomes the love of Marius (a young male protagonist). If I am not mistaken, she has only one solo song as an adult in the musical ("How strange, this feeling that my life's begun at last..."), and this is pretty much the way Cosette is shown in the book. For she never does anything (almost), never has any opinions about anything, never asks about her past or that of Jean Valjean. She and Jean Valjean spend days at the Jardin du Luxembourg sitting on a bench doing nothing (how boring that must be!) - I don't even recall any references to either of them reading a book there. She and Marius fall in love before they ever speak to each other (more or less). It seems that Cosette's sole raison d'etre is to be the "perfect" and "unspoilt" object of Marius's love and Jean Valjean's care and devotion. I suppose that is similar to how women are portrayed in many other 19th century novels (though Cosette takes passivity to the extreme). But, say, in The Three Musketeers, Constance Bonacieux takes an active part in politics and the intrigues (not to mention the Milady), so it certainly wasn't impossible to imagine women doing something in those days. And the plot of the The Three Musketeers is only marginally more fantastic than that of Les Miserables. Yet, somehow, only the latter is considered "serious literature".