Paizo Publishing will release Pathfinder Unchained, a 256-page hardcover of optional rules that change some of the fundamentals of the Pathfinder RPG, in April 2015.  Among the optional rules will be redesigned barbarian, monk, rogue, and summoner classes; a new action economy; new ways of designing monsters and treasure on the fly; a new resource pool for martial characters; and a new system for modifying spells with powerful spell components.

Players can pick and choose the systems they want to change in their game, from minimal changes to a new play experience. 

For an overview of Paizo’s plans for 2014, check out our interview with publisher Erik Mona (see "Paizo's Erik Mona: The ICv2 Interview").