A log book is a type of DIARY that is used to record important information. It is often used in the maritime industry, aviation, and other transportation industries to document events, activities, and changes in the operation of a vessel or aircraft. Log books can also be used in other industries to document events, activities, and changes in the operation of a business or organization. Log books are typically kept for long periods of time and can be used to provide evidence of activities and events that have taken place.