Originally titled Black Maria (because she is like the plague) but retitled because of unfortunate implications, Aunt Maria is a book by Diana Wynne Jones following Mig (real name Naomi, but she prefers Mig), her brother Chris, and her mother as they all move in with the dreaded Aunt Maria after the apparent death of Mig's father.
Maria is every passive-aggressive, deplorably saccharine matriarch you've ever hated. She is everyone's evil mother in law. She is all backhanded compliments and false-advice and guilt-trips. On top of all that, she also has some very outdated ideals that she enforces with a cold, sugarcoated fist. (Girls shouldn't wear pants. Boys get chocolate while girls make do with lesser candy. Children ought to be seen and not heard. Etc.)
At first, Mig and Chris are the usual sort of miserable at Maria's house-- the kind of misery that comes from being around overbearing relatives. But slowly and surely, they start to notice odd things around the little town of Cranbury. Why do all the kids here act the same? Why do all the townspeople seem to kowtow to Maria's beck and call? What is with the little cult of equally-overbearing ladies that flock around Maria? Why is Mig and Chris' mom acting more and more like the Stepford wife Maria wants her to be? Why is there a mournful ghost appearing in Mig's room, and what did happen to Maria's daughter?
What follows is a story with unwilling lycanthropy, time travel, murder, shape shifting, mind control, and magic.
This is what I mentally categorize as one of Diana Wynne Jones' "small" stories (Like Wild Robert, The Ogre Downstairs, and Enchanted Glass). The book is short and self-contained. The plot isn't as twisty as some of Jones' stories, but it's got the Jones' charm. Mig and Chris are realistic kid characters-- which is no surprise. Diana Wynne Jones had a way of writing sibling characters that always struck me as super realistic. Maria herself is despicable, simply because there's a chance you've probably met a Maria before (sans magic, probably).
This book is a quick, entertaining read. It's a kids book, but I first read it when I was sixteen and liked it. It's not as ambitious as some of her other books, but it's fun and short.