I've only had to use our logbook in an 'official' capacity once -- an
insurance company wanted a page. We were giving some folks a ride to a deserted island, who had travelers
insurance, and they
lost a bunch of
camera equipment when a wave filled the
cockpit and drained through an open window onto the quarter berth. They needed the page for the insurance company to pay them for their cameras.
Ours is very informal, a bound book of blank pages. It holds everything, to-do lists, notes on
navigation (more scrupulous when we are bored enough to be traditionally navigating),
anchoring,
maintenance, people we meet, communication between watches, and etc.
The only structure is, on
passage, we make columns on the right side of the book for
navigation notes (time, velocity, direction, pressure,
wind speed and direction), and keep the left side free to talk about the cat, dinner, or doodle.