I think this is the first book-to-movie adaptation where I preferred the movie. This book was honestly meh, and my original rating from middle school is fairly accurate. I'd give it 3 stars though, as it was emotional and classic coming-of-age. My biggest complaint were the alternating four POVs, mostly because they all sounded and felt the same. And there was no transition between them!! It was as jarring as an old rollercoaster. That part drove me nuts and pulled me out of the narrative every few pages.
The movie created more distinct personalities, and dare I say, more interesting stories for the individual girls. I felt that the book was lacking a bit in making the plotlines complex enough to justify a 350 page book, but some of the changes in the movie--namely, Lena's entire plot basically--made her story more captivating. Lena's was my least favorite in the book but one of my favorites in the movie (and not just because of Alexis Bledel, my Gilmore Girls queen).
On the flip side though, my favorite story to read about in the book was Bridget and her part in the movie was heavily watered down. I felt that Bridget had the most complex character and backstory, with Carmen as a close second, so I was disappointed by that adaptation. I really enjoyed the movie, however, if you couldn't tell, so I highly recommend it for a great story. I'd pass on the book if you're looking for something fun and intriguing to read though. I'm not sure I'll continue the series.