This is a movie that really doesn't know what it is. For one thing, it seems to try and hang on to some parts of the story by Dumas, and yet it also is an entirely different story. Seemingly, the only real similarities are the names of the characters. This movie would be much more effective if it was entirely its own story, and not using the names of the famous characters. The reason? This movie totally dashes the names of those characters.
The most unsettling part for me was the fact that the Three Musketeers are nothing like themselves. Porthos is not the least bit arrogant or over-the-top. Aramis isn't religious at all. And Athos does not even remotely resemble the character in the book. Sadly, Justin Chambers makes a better d'Artagnan than Chris O' Donnell, but only because he doesn't do any acting at all, which is better than the profuse overacting of O' Donnell. And Stephen Rea is a good actor, but his character isn't remotely as menacing as Richelieu should be.
With all of that said, if you just view it as a movie, and try to block the actual story out of your mind, it can be entertaining. The fight scenes are very well done, and the pacing keeps the viewer interested. Perhaps this movie could have been really good if it was about the story of a musketeer NOT named d'Artagnan, and his unique adventure. But since it tries to be an interpretation of Dumas, it falls miserably short. As a movie, it is so-so, but as far as an interpretation of the famous story, it is absolutely terrible.