I liked Shirley from the moment she turned in her "What I did with my summer vacation" paper and got a D for writing fiction (okay, she was telling the truth, but still. . . ). She's an insightful narrator with a touch of cynicism and just enough hubris to make it clear she's human. She reveals herself well in her narration, and describes other characters, inside and out, with a few well-chosen words. An example I liked was when she notes that the principal looks especially harried because "his eyeglasses sit on his nose like they want to escape his face."
One quibble: Shirley herself is 14 (according to the blurb), and although the opening line speaks of her 8th grade English class, she apparently attends a high school. At 14 my sons started 9th grade (which unlike 8th is commonly in a high school), so I did wonder if this was an error.
The story is well-written and fast-paced, the language is imaginative, and the denouement is reasonably surprising. A dry sense of humor kept me smiling, and I think this will work very well for the kids, too.
My biggest issue is that the book is just too short! I'm just starting the next book, but it, too, clocks in about 10,000 words. Since the writing style of the books is firmly middle-grade (and an 8th-grade protagonist fits that very well, along with the minimal violence and clean relationships), that seems pretty short--more novella than novel. The writing should match kids at a pretty high reading level, so I hope that future books in the series are longer and more complex to challenge them more. Though Mr. Zackheim might be onto something, with some kids these days being too used to tweets to have patience for a longer story. Or to put it in a more positive light, sometimes kids just want a fun quick read that doesn't talk down to them (a lot like the adults). Shirley Link can provide just that.
Highly recommended for mystery fans of all ages from 9 or so up.