Eli Bendersky's website [read in Spanish]
It is surprising I haven't read this book before. Having very much enjoyed The Count of Monte Cristo I still dodged many recommendations on the Three Musketeers. Guess there just was always something else to read. Well, now thanks to my Spanish learning endeavors, I finally got to read it (I like reading books in their original tongue, and since this book is in French which I don't know, I figured it won't matter much which translation to read and the Spanish one was fine).
The Three Musketeers is a very vivacious and entertaining book. The plot circles around D'Artagnan, a young recruit in the king's guard forces, aspiring to become a "formal" Musketeer, his three Musketeer friends Athos, Porthos and Aramis, their squires and some of their enemies, most notably Milady de Winter.
The characters in this book are very well developed. The book is quite large (~900 pages) which gave the author ample space to build a unique personality to each one of the major characters. Milady is cruel and manipulative, Athos is cold and balanced - the reader starts to expect certain behavior from the persons depicted in the novel - a sign of a very deep acquaintance with them knitted carefully by the eclectic author. As a bonus, some interesting facts about the history of France are revealed.
As I said, The Three Musketeers is a big book, but one that flies quickly. The plot is captivating and flowing, encouraging to devour the book in a short time. Highly recommended.