The "Handbook of Usability Testing" by Jeffrey Rubin and Dana Chisnell is a comprehensive guide that offers practical advice on planning, designing, and conducting effective usability tests. The book covers every step of the usability testing process, from creating test plans and recruiting participants to moderating test sessions, analyzing data, and reporting results. Updated in its second edition to include modern techniques and technologies, this handbook is essential for designers, researchers, and product teams aiming to improve user experience. It provides actionable methods to identify usability issues and implement solutions that enhance the overall effectiveness of a product or service.