At times, reading Sarah McBride’s account of her first years in politics as an advocate for trans equalities, one is forced to realise how foreign a country the United States is, particularly in the endless moral optimism that bubbles through every page. Yet the agendas of trans advocacy in both the US and UK remain the same: basic respect, often in the face of cynical misrepresentation and open hatred.

The infectious enthusiasm of McBride’s approach shames hardened hacks in the movement here, perhaps because the battle lines in the US are so clear, whereas in the UK much of the constant attempt to take away even those rights that have been gained comes from people who describe themselves as feminists and progressives yet never pause to ask why they are getting so much support from the rightwing press.

Another area of difference is in the way the US political mainstream embraces – some would say makes use of – the young. McBride was engaged in politics long before she transitioned, working on the Democrat campaign for the governorship of Delaware. She went on to be student body president at her university, where she was so popular that, at the end of her term, her announcement of her transition to an openly female identity passed off fairly undramatically and with huge support from her peers. She then proceeded to an internship in the Obama White House. Even before she transitioned, there was a sense that she was a future star simply because of that passion and this was in no way diminished by her coming out.

Much of the core of the book is a detailed account of how Delaware passed a trans anti-discrimination bill in the face of hostile lobbying by the misleadingly named Family Research Council and the occasional obtuseness of local politicians. For anyone who has ever been involved in politics, this is genuinely thrilling. It captures that sense of having to keep an eye on everything and everyone, of needing to keep your own people on side and perpetually counting the likely votes, of watching out for supposedly helpful amendments that would actually sabotage everything you are working for. The chapter is paced like a thriller, as well it might be.

In all of this, she was backed by her parents and her political mentor, Governor Jack Markell, but her principal partner was the love of her life – a young trans man she had met during her internship, Andy Cray. They dated, worked together, started to plan their future and their political careers, and then he contracted aggressive cancer from which he died four days after they got married. This part of McBride’s story is hard to read. She manages to talk about love and death without being mawkish, partly because she is aware of how like the Hollywood version of her life her account inevitably has to be. It’s a salutary reminder of how much sentimental cliches overlap with everyday experiences. Her utter lack of cynicism serves her well.

She carries on campaigning, because it is what her late husband would have wanted her to do. In the presidential election of 2016, she knows what is at stake for the trans community – Republicans were promoting “bathroom bills” aimed at making it impossible for trans people to function in society because they’d be unable to use lavatories that tally with their identities. Trump was already indicating that trans people were one of the groups whose progress he was keen to roll back. McBride, at 25, accordingly became the first open trans woman to speak as a delegate at a major political convention.

This is a good book in all sort of ways but it is clearly a campaign biography aimed at whatever her next step turns out to be, as well as promoting an embattled community’s rights. Its introduction by Joe Biden feels like an anointing, one she has earned by hard work, passion and her survival in the face of bad luck.

What can we learn from her? Probably that social media clicktivism and even journalism are no substitute for political lobbying. If there’s a weakness here, it’s that McBride is a classic tall poppy who speaks a lot about the trans community without being especially engaged with it – she has much to say about talking to trans kids, about the future, less about long, boring arguments on committees for trans housing and health provision. That last may be a little churlish – this is a fascinating look at how progress gets made and the charm and passion that turn an American into a candidate.

Roz Kaveney is a poet, novelist and activist.

• Tomorrow Will Be Different by Sarah McBride is published by Penguin (£19.99). To order a copy for £16.99 go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99