There is plenty of literature. None of it necessarily agrees with the rest, but Agile proponents over the past 15+ years have produced a copious body of literature. If you disown all of that literature, then all you are left with is some pseudo-religious principles, tenets and values, which is not useful for someone trying to improve a development org. It also make evaluation of its effectiveness impossible as there's no agreement on what's being evaluated.
Living and breathing values and principles entails putting something in to practice which means you need to put a stake in the ground as to "how", instead of just repeating platitudes. If you can't find three people who all agree on what "living and breathing the Agile values" means, then you can't practice Agile at team scale.