Wintersmith: (Discworld Novel 35) by Terry Pratchett

Witches are odd.

That much is clear to Tiffany. But she likes them . . . in an odd sort of way. Just as she likes Roland . . . in a friend sort of way (which most certainly isn't odd).

But Tiffany hasn't really got time to think about Roland, because she has accidentally danced with Winter himself - the Wintersmith.

And now the Wintersmith has a bit of a crush on Tiffany.

According to her friend Daft Wullie, if Tiffany kisses the Wintersmith (an awful thought), her nose turns blue and fall off. According to the witches, if she doesn't shake off her admirer, there will never be another springtime . . .

'Characteristically entertaining'
Sunday Times