Bittersweet by Susan Cain review – a mawkish manifesto for the happy-sad

The author of Quiet again bangs the drum for the world's sensitive souls, but her unflagging earnestness is depressingly short of nuance and humour

Now then, on a scale of 0 to 10: do you seek out beauty in your everyday life? Do you know what CS Lewis meant when he described joy as a sharp, wonderful stab of longing"? Do you react intensely to music or art or nature? Are you moved by old photographs? Do you experience happiness and sadness simultaneously?

If your answer is emphatically yes to these and similar questions in Susan Cain's Bittersweet Quiz (I came to a jarring halt at the one about being perceived as an old soul"), then you will score highly and qualify as a true connoisseur of the place where light and dark meet". You are not sanguine (robust, forward-leaning, ambitious, combat-ready, tough), but bittersweet - and to be bittersweet means to be sensitive, creative and spiritual, with a tendency to states of longing, poignancy and sorrow; an acute awareness of passing time; and a curiously piercing joy at the beauty of the world". Bittersweet, writes Susan Cain with her startling sincerity, means the transformation of pain into creativity, transcendence and love".