Okay, it sounds corny. It's not. Alatriste and his closest friends come to vivid life on the page because Perez-Reverte takes the time to reveal their histories, and describe the political and cultural turmoil of this specific time in Spain's history. The stories are told by Inigo Balboa, the son of Alatriste's dead comrade-in-arms, as he looks back from old age at his violent and tumultuous youth. This enables Perez-Reverte, through his narrator, to put the actions of Alatriste, with his friends and enemies, into a deeper historical - and emotional - perspective. Think of To Kill a Mockingbird, and how Scout looks back from maturity at the events of her childhood, and how that adds to the depth of her - and our - appreciation for her father's heroism. The same dynamic holds here (I grant, in a wildly different context).
I don't mean to makes these novels sound too serious. They are truly literature, but that doesn't mean they aren't a lot of fun. Swordfights, duels, massive battles, daring rescues, evil seductresses, witty comrades and one great villain - these books are packed with the kind of action that brings out the 10-year-old in guys of all ages. Yes, I think these are guys' books. Alatriste is what used to be called a "man's man," and I don't know many women who would be interested. But no matter what your gender, if you stay up late because TCM is running an Errol Flynn swashbuckler that you have to see just one more time - the Captain is for you. I've read the first two novels - can't wait to start the third.