The newest roleplaying book from Paizo, Pathfinder Unchained, represents something of a departure for the game, the publisher, and the typical supplement. It’s the result of the company allowing its designers to “do what they want” with Pathfinder, unrestricted by backwards compatibility.
Pathfinder Unchained includes four entirely new versions of the barbarian, monk, rogue, and summoner classes; variant rules for multiclassing, alignment, and wounds; a simplified monster creation process; an alternative, stamina-powered combat system; and more. The book will retail for $40 in print, $10 as a PDF.