Faithful to the first book, Twenty Years After feels like part of it instead of a sequel; only with an interval of twenty years between the two parts. All the good qualities of Dumas' writing are present.

Very light spoilers follow:
I was very much annoyed with the character of Anne of Austria, featured in the first book as the prosecuted queen the 4 protagonists save. In the Three Musqueteers she was a noble but troubled being, now a vicious hysteric woman. It seems Dumas made this narrative choice to accommodate the rest of the plot. The main antagonist was also poorly conceived. Of course one could argue the true antagonist of this book is time, dishonour, disdain for the divine royalty that Dumas admired so much but his heroes always prevail.