Book excerpt: How Journalists Use Twitter: The Changing Landscape of U.S. Newsrooms shows how leading reporters and editors at four major metropolitan newspapers are embracing Twitter as a key tool in their daily routines and how the social media platform influences coverage. This book builds on social media research by analyzing newsroom work through the lens of four different communications theories—diffusion of innovation, boundary, social capital and agenda-setting theories. This book will be of interest to scholars of communication, journalism, and new media.