People underestimate how honestly useful Dumas is. Well, if you get the abridged versions, of course, nobody wants to read that optimized-for-line-count nonsense. Read up on it, his tricks to stretch dialogue into more lines are hilarious, to the point of his writing style changing (and characters with long names suddenly dying) when his publishers changed the rules.
The Musketeers (four, by the way, I counted) are a lot of fun, and worth revisiting if you just want some old-school adventuring, with Good Guys, Bad Guys, Evil Women etc etc. It also teaches you a surprising amount of history – I’m not sure when I would have learned of Richelieu, but certainly much later and less memorably.