To start with, it's not any random story, it's not even only a book series adaption, it's based on the author's real experiences as geek discovered as model. I really love all six book installments, including the three specials, it's my favorite book series.
I only got access to Netflix to watch this adaption. It's here only based on book 1, a book I know by heart. But they also used some ideas and characters from later installments.
To start with, it's definitely aimed for a young audience, reminding me of my favorite teen romance comedy movies, such like Monte Carlo, Never been kissed or Cinderella Story. It's definitely a Cinderella Story, a fashion fairy tale. Harriet's journey to try to make her life better, with some unexpected magic from a "fashion fairy godmother", a beautiful dress, a prince Charming, but still on a journey to discover herself and to love herself. Somehow this adaption feels in comparison to the book like the Disney Cinderella live action remake in comparison to the 1950 animated movie. There's more depth, more romance, yet, to be honest, it's definitely not literally the book (I understand some changes, some less...). For fans, there are lovely references and it's so nice that Holly Smale, the original novel author, was co-author of this series, Certainly, the book was not easily to be turned to movie, much with inner reflection, here seen as a kind of voiceover. The original book is definitely recommended, perhaps not as much realistic or mature, yet, somehow more quirky, with Harriet being bubbly or sometimes more grumpy etc., with some ideas perhaps better to grab as presented here casually...