I read "The Count of Monte Cristo" in approx. 10 days and, at the end, had sore red eyes because I did not blink while reading it. From the beginning to the very end I loved it.
It was originally written as a serialisation which is why it is lengthy and sustains interest from one chapter to the next and, therefore, to the very end.
Primarily, the story is about a man's revenge but it incorporates so many other things. It is about travel and adventure (which for a 19thC reader was intriguing, but is also for today's reader), disguise (and deception), morality (putting right an injustice and the consequences), romantic intrigue, religion (confession, forgiveness and Spada/Vatican riches), wealth and poverty, history and politics (Napoleon's escape from Elba, girondiste v jacobins), justice (courts and duelling/sword-fighting), social etiquette and graces (equipages, dress, being seen at the right soirees, etc.), disgrace (being made bankrupt), scandal (burying a live baby), and even some comedy (satire).
Overall, the prose moves along very easily, though there are occasions when some dialogue is just a bit too long. The translator of the book also explains that some of the dates can be inaccurate, which can make the reader occasionally lose the chronological thread, but it is minor in carrying the story along.
I recently visited Port Marly (France) to see Alexandre Dumas' home, which is named "Chateau de Monte Cristo" (Monte Cristo in reality being an Italian island in the Tyrrhenian Sea) and Chateau d'If, but found the locations of the novel much more interesting.
In the 800+page novel there are more twists and turns than the recent filmed version can begin to include.