Before Ava DuVernay became the poster child for inclusion and diversity in Hollywood (a double edge sword, I'm sure), she nevertheless proved herself a very precise and insightful documentarian with this film.

The title refers to the amendment to the US Constitution that abolished slavery, and Duvernay makes the case that for millions of African Americans on the ground rather than in the hallowed halls of law and order, nothing's really changed.

Her contention is that the history of institutiuonally entrenched racism in the form of various wars on drugs etc, has led to a form of new slavery with the disproportionate number of American blacks in the prison system.

She collects together a number of intelligent, graceful black leaders to weave her thesis, and it's hard not to be won over by her message that little has really changed for blacks in the US in centuries.

And in talking about what a huge for-profit industry American jails are, it's further vindication of stuff longtime conspiracy nuts like me read decades ago.

How you take it will probably depend in large part on your politics. In some measure DuVernay will be preaching to the choir as right wingers don't tend to respond to this kind of thing at all, so at best it's a galvanising argument for what you already vaguely know about America, put together in a cohesive whole using the skills of a journalist.