Excellent book. Amy and Clarissa are two ordinary little girls who daydream about an old witch. Amy banished her to a glass mountain so she wouldn't be wicked, only to come out on Halloween when she is good. But being there is lonely, and the two soon populate the glass hill with others to keep her company: a little witch, a baby witch, a spelling bee, and a mermaid. Reality and daydream blur though, as both the two girls visit the glass hill, and the witches visit them on Halloween.
I wrote in my review of May Bird Among the Stars
that tone is one of the hardest things to get right in fiction, but the tone of this is wonderful. Her choice of words and descriptions create a magical and almost mythical world even when the description of it is our own mundane one. The Halloween night describing child trick-or-treaters in particular was a very evocative passage, and it really captures the feeling of childhood-the imagination and the feeling of a magical world.
I can understand people might not like it, because it's very surreal at times, tends to be repetitive, and the dialogue is quirky (although not in a dated sense, reflecting when it was written.) But for me, the writing, tone, and characterization made of an excellent reading as an adult, and I regret having never read this as a boy.