This is the third of the Adventures of Captain Alatriste.
This novel concerns Alatriste and Inigo's experiences in the war in Flanders in 1625. It doesn't really have the swashbuckling style of the first two, instead focusing on the brutality of that era's warfare and how this effects Inigo. His own experiences, and Alatriste's example, are clearly forming the man he is to be. The novel feels like it's an interlude in the overall story of Alatriste, which will continue when they return to Spain.
The action is exciting, and works despite the lack of a villain to blame it all on (although the evil Italian assassin gets mentioned in a letter from Madrid). It's interesting to read a purely military adventure novel, without the romanticized escapades that I'm used to in Cornwell's Sharpe books, for example.