Joan Aiken is always wonderfully inventive and playful in her short fiction. Disregarding any notion of genre boundaries she segues between comedy, whimsy, fantasy, magic realism, social commentary, and, in her adult stories, horror and SF, sometimes having a go at all of them in one tale. It doesn't always work, but even in misfiring stories (which can end up taking the fairy story into silliness and terrible puns), she is always testing out new ideas. There's more originality and vivacity in the best stories here than you'll find in the work of many more lauded authors.
This collection is uneven, but it's uneven because of Aiken's refusal to take the easy option. Like any good witch, she's always willing to drop something else into the cauldron and her risks usually pay off. Aspects of the stories have dated (inevitably - the collection came out in 1969), and for good or ill, we tend to treat children very differently now. That aside, I like this book very much though and hope I'll soon be reading it aloud to the sea while Morwenna thrashes about in a nearby thorn-bush.