Slicebooks, a startup that enables publishers to "slice," "remix" and sell content on its platform, announced that it has added content from six new publishers— Lonely Planet, Globe Pequot, FranklinCovey, Rowman & Littlefield, NBN, and the Independent Publishers Group. The additions bring the total number of the company's publishing partners to 280, just weeks ahead of the official launch of the Slicebooks retail store on May 29 at BookExpo America.