Boxers & Saints are companion pieces. Boxers weaves a fictional tale set in the Boxer Rebellion in China in 1900, which was the uprising against foreign Christian imperialists. Boxers is told from the viewpoint of Little Bao, a man who joins the rebellion, and eventually becomes a leader. Saints is about Four-Girl, a confused and mistreated young woman who joins the Christian missionaries as a way to help the people around her. Both Little Bao and Four-Girl believe they are on the right side of the war, and both are willing to do everything in their power to be on the winning end, although they go about it much differently.
Yang's drawing style is well-suited for children's books; while I wouldn't recommend this set of graphic novels to children, I think the ease of the drawings pairs well with the violence of the story. If Yang had a more serious style, it might be too much for the reader to take in. He allows for comedic breaks, and brings a lightness to the Boxer Rebellion that many graphic novelists couldn't. He doesn't make a joke out of the Rebellion itself, but he gives the characters personality; they're not just members of one side or the other. They're people who made choices based on what they thought was best.
Boxers & Saints are available by themselves, or as part of a set. I recommend the set; it's more interesting to see both sides of a story than just one.