This is the second Dumas work that I've read after The Three Musketeers. What I find interesting about Dumas is that there is a general popular view that his work is literature but, in fact, it is very much genre fiction of the 19th century.
Dumas was a bit of a hack and churned out his work. He could churn it out effectively, but it isn't great writing. For instance, this book has two beginnings. There is the first 30 chapters or so, which are what set up the revenge story of Edmund Dantes. We are then introduced to Dantes as the mysterious Count of Monte Cristo, but we already know who he is and what his background is. This would be just a weird inexplicable choice, but it turns out that the book originally started around Chapter 30 and then, in response to criticism from a collaborator, a new beginning was written, but Dumas did not bother to rewrite the old beginning. It's all competently written, but that choice shows that it really was writing by the word. Being paid by the word, does make certain 19th century books too long, I'm looking at you Dickens, but Dumas is the worst offender. The Three Musketeers was enough to see that Dumas suffers from this problem.
If we properly evaluate this book as genre fiction (an adventure story), then how is it? Dumas' ability to write an OK character or put together an OK sentence or an OK scene is certainly there. There are, in particular, quite a few striking set pieces. It's here that Dumas really shines: The Count in his grotto, or the escape from the Castle D'If are good examples. Dumas is certainly a competent and entertaining genre writer, but I would not put him amongst such giants as Hammett, Burroughs, Stephenson, Fleming or Lovecraft. He is more of an entertaining read. I don't know that I will ever read Dumas again for the simple reason that his books are far too long for the limited rewards that he provides. He is for me more like Howard or Chandler, but they had the good sense not to write books that were a 1000 pages long, so you don't find yourself wondering when it will end. He does manage to sustain the length through having a pleasant and easy prose style.
The book is really an escapist revenge fantasy. It reminds me a bit of a more literary E.E. "Doc" Smith in its writing style. The life that the Count leads as he is embarked on revenge is pure wish fulfillment. For instance, there is a throw away piece about the Count having six of the fastest horses in the world that are black with identical white stars on their foreheads. This is the 19th century equivalent of the Lamborghini collection that has been specially modified by the manufacturer. The other characters are stereotypes and the Count moves through this fantasy world, animating it. The book itself is more a forerunner of television and movie writing than genre novels and I could see Dumas, if he were alive today, writing for CSI or some such thing.
Dantes is a well done character, although not a really well done character. He is not dark enough for someone consumed by revenge that much. Dumas goes to extraordinary lengths to keep the Count from getting his hands dirty. He is very punctilious for a character consumed by vengeance. He also never really does anything very bad or very cruel, but in a vague way just sets chains of events in motion. He is a kind of Disneyfied Machiavelli and is just an escapist fantasy character and nothing more. It's funny that the book is considered great literature. For instance, if you compare it to Shakespearean works on revenge such as Hamlet, Lear or The Merchant of Venice it is not only not in the same league you cannot even see Shakespeare's league from where it is. Presumably Dantes' name is meant to invoke the Divine Comedy, but in the end it is a soft and snuggly retribution that we see here for the most part, although there is a death of a child which complicates things a bit.
Having said this, if you treat the book as an escapist adventure story with nothing to say, that is as light entertainment, then it is reasonably good light entertainment. It is not a must read by any means, but it is pleasant enough. If it was shorter, it would be a good way to start people reading 19th century novels, but it is a bit too long for that purpose.
OK, but I would read Robert Louis Stephenson first.