There's excellent documentation online, including a teacher quick guide, provided by the user and developer community. Being online and digital, this resource is updated daily and keeps abreast of Moodle developments as they happen - with far more details than any book could provide.
Most users find the Moodle interface intuitive which helps reduce the training requirements but we can provide Moodle training and advice to all or staff, both on line and in face to face settings.