They'll Never Catch Us is a story we've seen a million times before: Unsolved murders in a town where nobody is quite what they seem. This is not a problem though - Goodman writes characters that are complex yet easy to root for. I liked her commentary on sexism and the way young girls are forced to tune down their ambition into teenhood.
This being said, the book wastes its potential. It needed more time to develop the relationship between Mila and each Steckler sister for me to believe the events that went down could happen naturally. Their bond was underfleshed - Mila meets the girls, has a few deep conversations right off the bat, then gets killed. She is not given the pages she deserves as a character and plot device. Her friendship with the Stecklers is not the only underdeveloped relationship in the book; the majority of them are, such as Stella and Naomi or Ellie and Noah.
Furthermore, there is no reason Raven should be the killer, at least to me. I had suspected Noah's involvement in the whole thing from the start, and personally, I think if Goodman had gone with making him or people like him part of the murder, it would align better with the thematic elements of her story. The reasoning behind Raven killing Mila made absolutely no sense, and it felt like the author just added that twist for the sake of unpredictability instead of actual intrigue.
TLDR: Good writing style and interesting characters, bad follow-through and relationship-building. Also, it would've made more sense to have Stella and Mila fall in love than it did her and Naomi.