Rosemary's young, just at college, and she's decided not to tell anyone a thing about her family.
So we're not going to tell you too much either: you'll have to find out for yourselves, round about page 77, what it is that makes her unhappy family unlike any other.
Rosemary is now an only child, but she used to have a sister the same age as her, and an older brother.
Both are now gone - vanished from her life.
There's something unique about Rosemary's sister, Fern.
And it was this decision, made by her parents, to give Rosemary a sister like no other, that began all of Rosemary's trouble.
So now she's telling her story: full of hilarious asides and brilliantly spiky lines, it's a looping narrative that begins towards the end, and then goes back to the beginning. Twice.
It's funny, clever, intimate, honest, analytical and swirling with ideas that will come back to bite you.
We hope you enjoy it, and if, when you're telling a friend about it, you do decide to spill the beans about Fern - it's pretty hard to resist - don't worry.
One of the few studies Rosemary doesn't quote says that spoilers actually enhance reading.