The Merck Manual is a comprehensive medical reference book that provides detailed information on various health conditions, diseases, and treatments. It is widely used by healthcare professionals, students, and patients to understand medical issues and make informed decisions about health care. First published in 1899, the Merck Manual has evolved into a trusted resource, offering insights into symptoms, diagnosis, and management of illnesses. It is available in both print and online formats, making it accessible to a broad audience seeking reliable medical information.