No shrinking violet (nor Treehorn), Princess Hyacinth yearns to play outside—but she’ll float away! There’s no particular reason, but indoors she wafts upwards until the ceiling blocks her, and outdoors, the sky’s the limit. A wonderfully expressive illustration of Hyacinth dragging through the castle halls in her gravity-ensuring extra-heavy crown shows her pouting mouth (no eyes—they’re buried under the crown) and her huge, downtrodden shadow on the wall. Smith’s elegantly cartoonish brush-and-ink character survives an exhilarating scare involving a kite, a rescue and a newly formed friendship. Heide’s prose takes off just when Hyacinth does: “She whirled and she twirled, she swooshed and she swirled….” When Hyacinth soars free in a vast pink sky, her figure is tiny and three balloons follow behind, creating a scene of breezy adventure that also feels delicate. Oil-paint backgrounds (shafts of light; antique-hued balloons; soft animal topiary) glow behind the pointy-nosed, active characters. Molly Leach’s clever design shows the word “up” repeatedly rising, and one sentence levitates partially off the page—naturally. (Picture book. 4-7)