This book is a role playing introduction for an acting class. As such, it's about real enacting on a real stage. It is suitable for live roleplaying (and maybe freeform) but it is not designed for coach potatoes sitting round a table looking for profund rule discussion and a challenging dice war.
Forsooth uses a GM-less system where the players agree on a historic background before they begin. Playing followings the rules of a theatre drama in lines of the stage plays by Shakespeare.
To have fun with this you need a group of people with knack of acting. With some knowledge of Shakespeare plays and having some gusto for histrionic gestures, you could have a stunning evening with Forsooth!.