With a good story full of adventure, action, and intrigue, plus a very good cast, "The Son of Monte Cristo" is an entertaining and enjoyable movie. Louis Hayward and Joan Bennett work well in the lead roles, and George Sanders is always a threat to steal any scene he is in. The story stands on its own, since the only connection it has with the often-filmed "The Count of Monte Cristo" is the main character's relationship with the previous Count. So there's no need to be familiar with the original to be able to enjoy this one.
Bennett is effective as the spirited Grand Duchess, and Hayward has a juicy role as the young Count, which gives him the chance to assume a different persona every so often during the course of the story. As the brutally ambitious general, Sanders's appearance is quite a bit different from the more familiar look he has in his best-known roles, but his voice and mannerisms are easily recognizable, and he comes across with a good blend of suavity and menace.
The story has the Grand Duchess being held at the mercy of the general, with the Count eagerly getting involved in the fictional country's affairs. The story has many turns and mild surprises, and it does a rather resourceful job of coming up with new predicaments and developments to keep things going. Most of the plot devices are familiar from other sources, but they are pieced together with skill, and its very good as light entertainment.