HarperCollins editors Robert Jones and Gail Collins preempted a book on the emotional challenges faced by black women in America with a mid-six-figure, world rights bid to agent Todd Shuster at Zachary Shuster Harmsworth. It's by a pair of African-American authors, Kumea Shorter-Gooden, who is a California psychologist specializing in women's problems, and Charisse Jones, a correspondent for USA Today. The title is Shifting, and Harper plans to publish about two years from now.