I've read half the book, and the stunts are the very best part of it
You can choose half your POW in stunts, they then cost a variable number of POW points to activate, and you can really fine-craft a peculiar persona through a certain selection.
For example, a lot of stunts allows a special fencing move, if you envision your PC as a swordmaster you could choose "Deadly Duelist", "Flashing Parry" "Initial Carving" and "Riposte", while a burly pirate could use some of the "Fists Like Ham", "Countenance Like A Devil", "Hardy", "It's Just A Flesh Wound" and "Mighty Blow".
During the round you spend the power points, like a sorcerer would to cast spells, and activate the stunt; it's simple, merges quite well with the BRP default system and is very swashbuckler style