I've loved the Musketeers ever since I first saw the 1973 movie but haven't gotten around to reading the actual novel until now. I even managed to read The Man in the Iron Mask first, which should have tipped me off more about what to expect. But seeing how that book is described as a darker turn, I was still surprised about how the main characters act in the book.
Namely, they're a bunch of douchebags.
They get into duels (which is illegal) and then have to fight the guards (who are trying to arrest them for doing something illegal) and maim and kill people without any sort of consequences. At one point Athos gets goaded into telling a dude his true name before a duel, only to tell him that now he has to die and go about killing him. Porthos is leeching off a married woman, Athos became a Musketeer after doing the French equivalent of an honor-killing and they all mistreat their servants. Athos beats his if he speaks to him and they all recommend that Dartagan does the same. They financially take advantage of anyone they can, cause havoc everywhere they go and kill a lot of people super casually.
That being said, I do love them for it.
My friend and I used to describe them in the movie as "Varsity Stars who can get away with everything" but I had chalked a lot of that up to being characters in a Richard Lester movie, not the original novel. It was fun to read about them holding wine cellars hostage, putting in no effort to avoid violence and not realizing that rent was something they had to pay until their landlord informed them. They're not great people, but they're great to read.