I've never known anything like it. Even the arrival of Harry Potter and the Cursed Child in the West End didn't generate quite the excitement that the first preview of the hip-hop musical Hamilton has.

"Have you got tickets for Hamilton?" someone asked me anxiously yesterday. This was backstage at the Royal Opera House, not a place you'd necessarily think the staff would be concentrating on Lin-Manuel Miranda's musical about the Treasury Secretary Alexander Hamilton, the man on the ten dollar bill, when they have their own Nutcrackers to open.

"When are you going to Hamilton?" a friend in the park queried. "I've only got tickets for January." "Are you going to Hamilton?" another asked on the phone. Nobody ever asks me what I am going to see, even if it is as exciting Andrew Scott's performance in Hamlet or the opening of the Bridge Theatre.

Meanwhile, an orderly queue among teenage friends of my acquaintance has quietly formed in case my friend Susan can't go to the theatre with me on the night I am off to write my review. They know all the words to every song; a situation I can't remember for any musical ever. None of us have seen the show, but we know it is special and worth fighting to see. That's also unprecedented in my opinion.

So what is it about Hamilton that is causing this extraordinarily high level of anticipation? Obviously, in part, it is clever marketing. Social media is smartly abuzz with little films and teasers from the appealingly enthusiastic Lin-Manuel and the rest of the cast, building the wave of excitement, to flood tide levels.

But the fervour spills beyond social media and press reports, because people are genuinely excited. Hamilton is, even if you have only listened to it, a genuine groundbreaker. It changes the form. It has lyrics that read like poetry and tunes that make you want to punch the air; it has wit, scope and panache. Ever since it made its off-Broadway debut in 2015, people have been talking about it in the terms used for a great work of art.

But it is something more than a musical. It is a beacon of hope. By the single radical act of casting America's founding fathers as non-white men and telling their complicated story in a genre that is principally, though not exclusively, hip-hop, Miranda did the most remarkable thing.

He made a multi-racial, inclusive vision of the society that America is today reach back into its past. As Helen Lewis puts it in her excellent piece on Hamilton in this week's New Statesman: "The sheer ebullience of the soundscape is not enough to explain why it became a hit. To understand that, we need to understand the scope of its ambition, which is nothing less than giving America a new origin story."

This act is partly political. It is no coincidence that the first song heard from Hamilton was sung for President Obama at the White House – or that immediately after Donald Trump's victory, Vice President Mike Pence's visit to the show was greeted by an appeal by the cast, from the stage, for tolerance.

But it is more than that. It stands like a good deed in a dirty world, suggesting that a different view of past and present are possible. Its message probably shines brighter now than it did when it was first written. At a time of such confusion and doubt, it makes the case for idealism and striving for the best. Whether British audiences and critics will love it quite as much as liberal America remains to be seen, but we can all be glad that such a buoyant and brave creation is finally amongst us.

Hamilton open at the Victoria Palace Theatre on 21 December, and is currently in previews.