Actually, the 70's Musketeer films were very true to the book. And they also were very popular, and they've had the biggest influence on the film mythos of the Musketeers since their release. The reason Rochefort wears an eye patch in the Musketeer films started with the 70's version (it's a scar down his left temple in the book), and Rochefort's increased status as a villain came about from the 70's version.
Those are honestly still my favorite, the actions not too overblown, the writing is charming and fun, and it's old fashioned classic adventure cinema. I don't have a problem with steam punk, and it's an interesting angle, but there's a reason people say keep it simple stupid. Less is usually more. And I get annoyed that they're changing characters completely (like Buckingham being a villain).
Still, I'm more of a purist with this then most. If the movie is fun and not too mindless, I'll enjoy it.