YMMV, but I've noticed that you can actually read books in foreign languages quite enjoyably without a perfect grasp of the language. If the book grips you, words or even paragraphs you don't understand stop to matter. Sometimes it will take a couple of pages of "oh shit, I don't know what this is saying at all" before you get into it, though. (Reading it on an e-reader for the instant dictionary does help, of course.)

One of the interesting things about Monte Cristo and actually about a lot of 19th century French literature is that there's very little archaic French in there, and I found it easier to read (though still not easy!) than many modern novels that use French street slang / argot.