It's a 2.5, but I considered breaking all rules of arithmetic and rounding down because Barrie Summy clearly went to the Lisi Harrison school of pop culture references and passed with honors.
Okay, Summy's writing isn't THAT bad. Whenever the book gets into the plot, be it the mystery or the main character Sherry's budding romance, the like totally radical teen slang and pop culture references begin to even out, but these crutches to make Sherry relatable and appealing to tweens fall flat and make the first few chapters hard to get through.
The mystery is also perhaps a little too obvious. I'm not exactly in the target demographic for these books, but during the culprit's first appearance, I figured out exactly what was going on with only a few details needing to be filled in. It's good to have your mysteries be solvable, but Sherry focusing on red-herrings was a little frustrating.
I thought Sherry was a decent protagonist. She's got a lot of hidden depth to her and I liked how, from the early chapters we get to see how her mind works. She was written consistently as a creative, out-of-the-box problem solver who has good people skills but also fails to look closer at other people than surface level. She's a flawed protagonist who is quick to judge people, often based on appearances, and can be quite rude about those things in her narration but in a way that feels very true to your average middle schooler. Like, she'll nickname people "GI Joe" or "Monkey Man" in her head or talk about how ugly someone's outfit is. But this superficiality actually has consequences throughout the book AND she's willing to change her tune whenever she gets to know people better.
Because I bought the second book in middle school, I'm also going to read it, but I'm unlikely to seek out the other books in this series.
My analysis is that Summy definitely has talent for character writing but comes across as trying too hard to make her characters sound like teens to the point that it sounds borderline like a parody.