if cramponner and haschisch are the only words in that entire passage you would need to look up, then youll be fine reading les mis i think (im currently reading it in the original french, am bilingual and speak french daily at home, im loving the book so far but a lot of the older words i do have to look up). a 1600 page long book is a challenge regardless of language, so might as well read the original text for the full experience :)