From the announcement:
We told you yesterday to be looking out for a new free preview of Shadowrun, Fifth Edition, and that preview is now available (Battleshop, DriveThruRPG). While the first preview focused on the look and feel of the game, this one provides more rules content. It has a big load of the Game Concepts chapter, laying out the basic framework of the game, including tests, limits, attributes, uses of Edge, and so on. Enjoy!