18 year old Frankie Price has been living with her adoptive aunt's family for the past few years since her mother has mental health issues. She's very much the poor relation as her Aunt has married a rich man who has a successful clothing business. Frankie doesn't really fit in with her privileged, pretty spoiled, rich cousins. The one she feels closest to is Ned, who is a couple of years her senior. Frankie has romantic feelings towards Ned (this is not as weird as it sounds, as they are not related and the Aunts for years have stressed that they're not related to Mrs Price and her children).
A problem with foreign suppliers sends Frankie's adoptive uncle abroad and while he's gone his children end up preparing to perform at a music festival, in the company of the Crawfords, a brother and sister who are step-siblings of one of Frankie's friends.
One thing I really liked about this book were the quotes from Mansfield Park at the beginning of each chapter. These were relevant to the chapter at hand and highlighted which aspects were tying back to Mansfield Park. Many of the events from MP are represented; Fanny's horse riding exercise becomes Frankie's driving practice, the play becomes the music festival etc.
There are some differences too - the characters of Mrs Norris and Maria Bertram (Nerys and Mia) were massively more likeable than in Mansfield Park, and something that was largely glossed over in the original, the fact that Sir Thomas had slaves contributing to his fortune, is explored here a bit more, with Mr Bertram discovering that his clothing is being stitched by child labour and other unfair working practices in Mexico. Also, in Mansfield Park I felt there was a very strong nature/nurture debate which isn't present in this book.
There were other aspects that were different, but I felt kept Austen's themes intact; characters such as Henry and Mary Crawford are probably much more appealing to a modern audience than they would have been at the time and Fanny can be hard to identify with because she's so low-key. However, here Henry is a charming slime bag, his sister Alice is amusing but shallow and although Frankie is not accustomed to putting her needs first she's not a complete doormat and we see a lot of her thoughts, which helps the reader identify with her. The end of the book is wrapped up quite abruptly, which is a nod back to MP I could have done without to be honest, I'd have liked a bit more detail!
To get the full experience of reading Mansfield Park you are obviously better off reading the book itself rather than an update, but to get the gist of it, particularly for a younger reader, this book is a really worthy update.