More than 2.5 million children are homeless in the United States. Richard Schweid, author of the newly published “Invisible Nation — Homeless Families in America” (University of California Press), will lead a discussion of the book at 7 p.m. Tuesday at the Groton Public Library. Joining Schweid for the presentation will be Jeffrey Anderson, executive director of Mystic Area Shelter and Hospitality. Schweid visited five major American cities in researching “Invisible Nation” and will discuss the history of family homelessness — and what can be done about it. Anderson provides not just a professional but local context. The event is free and copies of Schweid’s book will be available for purchase courtesy of Bank Square Books. The Groton Public Library is at 52 Newtown Road, Groton. (860) 441-6750, richardschweid.com.