Warriors of God: Richard the Lionheart and Saladin in the Third Crusade, by James Reston. Faber and Faber, 2002.
Saladin became the sultan of a mostly-united Muslim world (where Shia and Sunni were conflicting even then). The European side was dominated by Philip of France and Richard the Lion-Hearted of England. Many others are involved, including brief appearances by Eleanor (Richard’s mother), John (his brother), and even Robin Hood. This was war, but politics certainly had its impact. The story is always interesting, though occasionally marred by flashbacks. Even 800 years later, we feel the echoes of this conflict.