Jane Austen rightly felt that Emma was “a heroine whom no one but myself will much like”. She might have been talking about the titular teen in Lady Bird. And Greta Gerwig’s Oscar-nominated coming of age comedy is certainly Austentatious.

Christine ‘Lady Bird’ MacPherson is seventeen, self-centred and lackadaisical. Crunch times are coming – qualifications, prom, college. But mostly she butts heads with her steely Mom, spends time with her best friend Julie and scoffs communion wafers in the backroom of her Catholic school. Behind on her grades but with a spark for performance, Lady Bird – her given name, “I gave it to myself; it’s given to me by me” – gets a song and dance part in the play. But she really hankers after the leading boy; or maybe the pseudo-intellectual rich kid sleezer. Whatever, reality awaits.

Saoirse Ronan (Brooklyn, Atonement) is spot-on as Lady Bird, catching the curve of writer-director Greta Gerwig’s snappy dialogue, whether cussing her hard-working mother or dissing an anti-abortion guest speaker. But Ronan’s Lady Bird is never totally unlikeable despite her sass and selfishness. For two reasons – Ronan’s flesh and blood performance, and Gerwig’s decision, Austen-like, to make this a genuine growing-up story.

And that’s the most refreshing thing about Lady Bird. This is a family movie in the fullest sense. Unlike the hipster teen comedy Juno, winning the Oscar for best screenplay back in 2008, or the Emma update Clueless, Lady Bird isn’t only about the girl. It’s equally – if not more – about Lady Bird’s impact on her mum, dad, brother, sister and best friend. Gerwig’s movie speaks to a bigger truth. Not just about losing cherries and gaining wisdom, although it is, it’s about loving and living with a undeveloped person and seeing her grow.

Chucking herself out of a moving car when her mum gets too much, Lady Bird is a quixotic drama queen. Head-turned by the smarter set, she ditches her more studious and less attractive friend for palpably pretentious slapheads. You can see where it’s all headed. But Gerwig’s masterstroke is how she gets you there. Lady Bird isn’t a conventional, by-the-numbers teen movie. It’s a deft, believable, and somewhat spiritual film. Others would’ve used the church-school setting for jokes and teenage kicks against the pricks - celebrating the sinner in the saint. Gerwig does the opposite, and takes the iconography and church music on its own terms. And that’s bold.

Funny and engaging, it’s a brilliantly acted movie and Lady Bird’s friendship with Julie is infectiously entertaining. The over-use of soundtrack songs to give emotional clues is a shame, and the only conventional thing about the film.

Close to Pretty in Pink in seeing teens from the parents’ perspective, Lady Bird is closer still - almost a prequel - to Gerwig’s and Noah Baumbach’s Frances Ha. Assuredly it marks the thirtysomething Gerwig out – like a modern-day Austen - as an accomplished artist dealing with imperfect women finding their place in the world.

Barbed wire words, laugh-out-loud put downs - Lady Bird is breezily entertaining and painfully on the note. But a faultlessly credible cast ensure that Gerwig’s film is about much more than that. Family, friendships, hardship, loyalty, sexuality, gratitude. Which is to say it’s a movie for teens, mums, dads, guys, girls… And Lady Bird’s trick is that each will get something different out of it.

So when you wonder how a film about a stroppy teenager can possibly be Oscar-nominated, now you know. Jane would understand.

Watching Lady Bird is an odd experience. This perfectly formed, charmingly constructed, quietly devastating film is not about anyone other than the central figure of Lady Bird (and, more loosely, the film's director, Greta Gerwig). Yet the film offers a reflection of teenage years in the relationships that make up the bulk of the film which gives it a universal quality.

The film's narrative initially seems slight. We follow Christine McPherson, who has renamed herself Lady Bird, through her final year at school. The film explores first love, heartbreaks, college applications, student drama, without every feeling the need to artificially wedge a clearly defined beginning, middle and end onto this. The film washes over its audience with a warm glow, partially thanks to its Sacramento, California setting.

One of Lady Bird's great assets is a stellar turn from Saoirse Ronan (one of the best actors of her generation). Ronan gives a naturalistic, grounded performance, one ripe with subtle complexities. And that flows down through the cast, with almost none of the parts feeling throwaway, no matter the length of time on screen. Particular standouts are Lucas Hedges as Christine's first love, Beanie Feldstein as her best friend, and Tracy Letts as her father. Each give beautifully observed performances even when they filter out of the lead character's attentions. Yet at the film's core is a richly observed mother-daughter relationship, aided by a career best performance from Laurie Metcalf, who simultaneously manages to be a warm presence and a fearsome matriarch. The scenes between Ronan and Metcalf crackle with an electricity.

The film is filled with acidicly funny one-liners, yet has a sweetness that sets it apart from more sarcastic examples of the American indie comedy genre. It treads a fine line of emotional trauma that often sneaks up on a viewer. A conversation can change gears within sentences, with the film's ability to wrong foot its audience showing an impressive confidence. There is a post-break up scene that devastates but for a completely unexpected reason. It is this that makes Lady Bird feel like such an accurate reflection of the world around it. It is admirable that when the film reaches its conclusion its lead character is not fully-formed. This film is a single snapshot of her life; there are always more that can be taken.

Writer-director Greta Gerwig (who is only the fifth female nominee for Best Director in the Oscars' 90 year history, a terrible statistic) displays the skill of someone who has worked in films for over a decade. Lady Bird may be her debut but it shows a boldness that masks this fact. The film is tightly paced, constantly moving forward and rarely lingering on the latest incident to impact Christine. It is a story steeped in modernity, almost the perfect response to the #MeToo eruption, with women working both in front of the camera and behind it. This is a film that will rank amongst the best of the year and is a must-see, one that will tug at your heartstrings and make you dwell on just how annoying you must have been as a teenager.