Although the rest of the series gets so much better, this first book is lovely and engaging. We are introduced to Hilda, a young blue-haired girl (perhaps around 10 years old in conception) who defines herself as an adventurer, taking every opportunity to explore the wild and put herself in perceived-but-safe harms' way. Fortunately, she lives in a fantasy land, with trolls that turn to stone in daylight and giant floating puffball mammal creatures, and the woodman. She lives in a remote cabin with her mother, who appears to be an artist or designer or architect of some kind. She does not show particularly good sense, nor does she think well in advance, in a way that is typical for her age but which is not reflected in children's books very well, I think, given how frustrating and terrifying this behavior is to adults.
This is the shortest of the Hilda books, each of which is a self-contained but continuing story so they should be read in order. The art develops over the course of the books, so if there is anything that irks you visually here, rest assured that it will likely change. The character models (Hilda, her mother, and Twig) change notably across the first three to four books, softening overall and becoming more animation-friendly, I think. The later depictions are what you will see in the animated Hilda series.