These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Are Claire, Dylan and Kristen bullies or bully victims who play along with Massie and Alicia because they're so afraid of them?
The final books in the series very strongly hint towards this.
Audience-Alienating Premise: It's a series told from the Alpha Bitch's point of view. If you don't like that character type (it's nearly universally despised) there's a good chance you won't be interested.
Deader Than Disco: Seems to have become this in recent years, for several different reasons (the pop culture references aging badly, society frowning on anything bullying related, etc.). It pretty much went from a New York Times bestseller to a mainstay in second-hand stores.
Growing the Beard: Starting with These Boots are Made for Stalking and My Little Phony. There's more meaningful character development (particularly with Claire, Massie, and Layne and Cam[!]) compared to most of the other books and a lot of the Flanderization that was going on gets undone - in particular, the characters actually start to mature and Claire finally grows out of letting Massie remold her into yet another PC clone and tries to stand up to her. In short, the series finally becomes the series people were actually expecting/hoping for. Unfortunately, it came too little too late, in the third-to-last and second-to-last books out of a nearly two-dozen long running series.
Harsher in Hindsight: Recent events having to do with bullying have made this series incredibly hard to enjoy. The treatment of Claire in the first few books goes from Dude, Not Funny! to downright horrifying.
The plastic surgery jokes are this now that preteens getting them has been revealed to sadly be Truth in Television.
Hollywood Pudgy: Dylan. Even the girl portraying her in the offical photos is incredibly skinny, to the point of anorexic.
Nausea Fuel: The author's Costume Porn is described as if the Pretty Committee are in their twenties when they are much younger, which makes it feel like Lolicon and can be very off-putting.
Portmanteau Couple Name: Among the genuine fans, Massington (Massie/Derrington); Clam (Claire/Cam); Dolert (Dylan/Plovert); Jalicia (Josh/Alicia); Closh (Claire/Josh).
Replacement Scrappy: Alicia tries to bring in In-Universe examples when she tries to form her own clique: "Strawberry" for Dylan, Kori for Kristen, "Faux-Livia" for herself and herself for Massie. It ends up failing miserably, partly because Alicia can't help but think of them as Replacement Scrappies for her real friends (and partly because the "knockoffs" are Too Dumb to Live)
Ironically enough these same "knockoffs" form Claire's own (very short-lived) "anti-"clique in My Little Phony.
When Alicia starts yet another clique (this time by stealing away the originals) Massie is desperate enough to outright hire her own Replacement Scrappies from a talent agency, this time handpicked based on not resembling the people they replace (though she can't help herself on some points, picking a girl known for starring in commercials as a soccer player ala Kristen who also co-starred with Claire on Dial L for Loser). It doesn't end well, for the exact same reasons why Alicia's first attempt failed.
The Scrappy: Cam tends to fall towards this, if nothing else dragging Claire down with him through her constant obsession with him.
They Just Didn't Care: Throughout the whole Summer Collection Series it's obvious that the books were churned out in a real hurry - in addition to the short page counts (the longest one is just over half the length of the shortest "proper" Clique novel) and the compressed publication dates (the whole collection came out over the course of Spring/Summer 2008), the series is rife if not outright pockmarked with obvious copyediting errors. That said, these (particularly Dylan and Kristen) are some of the best books in the whole Clique series.
There are various continuity and other errors throughout the whole series. In one of the books, Claire tips over a glass towards herself, but the stain ends up on Massie's dress. This happens over the course of consecutive paragraphs.