It's not available for over a month yet, but Paizo developer Jason Bulmahn is - along with most of the tabletop gaming industry - at the GAMA trade show in Las Vegas, and appears to have a finished copy of Pathfinder Unchained. This is Paizo's "experimental" book - it's Unearthed Arcana, if you will, although many people prefer to label it as a "Pathfinder 2 Testbed" (not that there's any hint that such a thing exists). "Within these pages, the designers of the Pathfinder Roleplaying Game unleash their wildest ideas, and nothing is safe. From totally revised fundamentals like core classes and monster design to brand-new systems for expanding the way you play, this book offers fresh ideas while still blending with the existing system." Due April 29th. Or right now, if you find Jason Bulmahn in Las Vegas.