Brain on Fire: My Month of Madness by Susannah Cahalan (Penguin, £9.99)

The author, a young journalist on the New York Post, wakes up one morning to find two red dots on her arm. She thinks she’s been bitten by bedbugs, so she calls an exterminator. He finds no bugs. Later, she feels “a terrible ache in the pit of my stomach”. More symptoms follow. She is overtaken by an urge to read her boyfriend’s emails. So she does. One of her hands goes “completely numb”. She experiences extreme mood-swings. She has a seizure. “Blood and foam began to spurt out of my mouth through clenched teeth.” What is happening? A medical mystery story, frightening and beautifully told.