Simple (Usually), Descriptive, and Illustrated
Remember how we said this is a book for/about kids over in the "Genre" section? Well, the simple writing style also helps convince us of this fact. By simple we don't mean dumbed-down, just easy to follow. For instance, we see Kipper, a likeable chap, describing Framley as: "'He's about the biggest, ugliest, laziest rat you have ever seen!'" (16.55). Yep—that gets the point across pretty effectively.
When the writing isn't simple, it's usually to make a mockery of fancy speech patterns. The queen of the cabbageheads, for example, can't be understood by many of her subjects because she talks like this:
"Thus we might alight and henceforth meander to yonder aperture to re-establish a harmonious, intergraded monarchical community, and go forth with our troglodyte agriculture." (29.8)
Um, say what? One of her subjects prods her to translate into common speech, though, so we can all catch up. Thank goodness.
While Alan Snow isn't huge on giving us every last detail about how characters look, we generally get enough of a description to form our own ideas with confidence. For instance, when Arthur first meets Willbury and his underling friends, this is what we are told:
There were two more boxtrolls sitting on a shelf, a small man with a cabbage tied to the top of his head, and an old man. The old man sat in a high-backed, leather armchair. He was wearing half-glasses and a gray wig and was smiling at Arthur. (5.9)
Mental image of Willbury and his crew: check. Ours is probably a bit different from yours, but the key details should all be the same.
Finally, we'd like to note that Alan Snow's illustrations contribute a lot to the book's style. They're fun little sketches of characters, settings, and scenarios. More complex than stick figures, but still pretty simple and cute, they definitely help demonstrate what's going on in the story. Like the writing style, the illustrations give you the essence of what you need to know about a character or a situation—the lines are clean, and some details are left to the imagination. In other words, don't gloss over the pictures.