When we say that this book is written with a childlike and simple style, we're not blowing it off. Not by a long shot. Instead, we mean that most of the book consists primarily of Shirley's thoughts, opinions, and experiences—and as such, the writing style should be childlike and simple. It's not about a sixty-year-old rocket scientist, after all.
Despite being only ten-years-old, Shirley calls 'em like she sees 'em, which means that we get her unfiltered kid perspective on all sorts of thing. For example, check out her assessment of her new principal:
There was something more foreign about the principal than about any other foreigner she had seen so far. What was it? It was not the blue eyes. Many others had them too. It was not the high nose. All foreign noses were higher than Chinese ones. It was not the blue hair. Hair came in all colors in America. (3.2)
We're getting this all straight from Shirley, literally hanging out with her as she tries to put her finger on what's so different about the principal to her. She isn't using fancy language or trying to seem older than she is—she's just a kid trying to figure something out, and the writing style follows suit. This is the case throughout the book, and as we learn about life in the U.S. at the same time that Shirley does, it's pretty easy to follow her logic. Importantly, this helps us appreciate that no matter where we're from, kids are kids at the end of the day.
This book isn't all words, though, and there are also drawings of Shirley's adventures at the beginning of each chapter, black-and-white sketches introducing what happens to Shirley in each part of the book. For example, when she meets her new classmates, we get a nice pic of Shirley all dressed up for school, staring at the strangers waving hello. The drawing gives us a sense of how isolated Shirley must feel. Not only is she shown off to the side (symbolizing isolation), she doesn't understand their mannerisms or language. Rough.
Occasionally illustrations come in the middle of the chapter, and when they do, you should probably pay close attention to them. This is because they only show up when something really important happens. For instance, when Mabel is finally nice to Shirley, there's a drawing of Mabel and Shirley huddling under Shirley's umbrella together against the rain. That moment is huge in Shirley's experience, eventually launching her whole sense of belonging at school, and the appearance of a picture mid-chapter makes sure we take notice of this development.