The play Les Miserables gives an excellent portrayal of the lives of people prior to the French Revolution and showed what led to that uprising. Historically, those are some excellent things to remember and focus on in order to prevent any sort of ruthless bourgeoisie coming to domineering ruling power again.
Additionally, and more pertinently for modern times, it portrays the struggle between the upper and lower classes. There will always be economic wealth and poverty, regardless of era or nation. This play gives insight into the desperation and severe want that these people experienced. This insight helps to understand the plight of the impoverished in the modern era, which is especially important for generosity, charity, and politics as well, since their plight is greatly affected by those things.