"The Son of Monte Cristo", "The Wife of Monte Cristo" and "The Treasure of Monte Cristo" are not by Dumas. They were written by Jules Lermina as a way to piggyback and profit off of Dumas' name and characters.

If you read them, you'll be disappointed. Let's say that everything that Dumas gave to the Count, Lermina took away, until he was a broke and lonely hermit back on Monte Cristo island.