Three Musketeers: by Alexandre Dumas, père.

Not only this tells one something about history, it also gives the window on the morals of the day - a male subordinate could plot and kill and rob in the name of politics until caught with his hands red or in pockets of another, but a woman unable to show all the pearls she had was more than a suspect, she was already condemned with loss of a pearl or two as undeniable proof of her adultery, giving no quarter to the whole possible spectrum of human relationships that span the gap between gift of pearls as a memento and an actual adultery, not merely a love of heart but an act physically committed.

And so with all the adventures of the musketeers and their success in reaching their destination and return, the most satisfying is the moment when the queen is able to show a full set of pearls, and the villain is accused of intending to present her majesty with extra pearls under an elaborate charade of making the king demand the queen show her pearls and insinuating the minister had two of them.

Second only to the superb, incomparable Count of Monte Cristo, and perhaps more fun in all its innocence compared to the tragic reality of the other, this classic.