With feelings so out of this world!

There is no right answer to this question such is joy of reading, rereading, death of the author and freedom of interpretation. I think the simplest way to figure out what the brick is about is to see what Hugo emphasizes and recurring threads he pulls on. In that regard it is actually easier to get at.

Between the living conditions (either by choice or by force) of many of our characters I think it is fair enough to write off this novel being a model of behaviour for the "miserables" of the novel. In the 19th century even now class divide is very much a problem. So it isn't for the impoverished and socially ruined, check. Rebellion at any cost? As most sensible people today Hugo concludes that people don't owe others their comfort and people are not oblidged to give up their lives in the name of social change. After all, any sensible person knows that is a collective effort and one can only affect so much. But, does Hugo think that the miserables by nature of being miserables are obligated to give up their lives? Also no. A radical stance in the 19th century and indeed, to an extent, even now. So if it isn't rebellion and it isn't sacrifice what is it? "To love another person is to see the face of God," (Les Miserables the musical). While it is unknown if Hugo ever wrote these words its intent is very much the core of Les Mis. I think, seeing as it isn't rebellion and it isn't demanding unwilling sacrifice.... that leaves us with one option, Les Miserables is about hope, love, the ebb and flow of progress and compelling those in positions to make real change to see the universality of everyone's humanity and make long-lasting change.