I’ve actually reread Diana Wynne Jones’s Charmed Life twice in recent months: once, to check it was about the right level to read aloud to my kids, who are nine and six. It was, so then I read it to them. Both times it was equally delightful, and I’m lining it up for a third go now, because I can’t think of anything that would cheer me up more.

Published in 1977, Charmed Life is the first of Wynne Jones’s books about a mysterious, brilliant enchanter known as Chrestomanci, all of which are excellent and unrivalled. This one, about Cat and Gwendolen Chant, two children who are sent to live with the great enchanter after their parents die, won her the Guardian children’s fiction prize. Amid a glorious list of former winners (Goodnight Mr Tom! The Owl Service! The Knife of Never Letting Go!), it’s probably my favourite.

Cat, whose real name is Eric, is small, rather cowed, and not particularly good at anything other than being friendly. Gwendolen, his big sister, is very pretty and has a “real talent for magic, dearie”, as Mrs Sharp, the somewhat shifty witch who takes the orphans in, puts it. She’s not very nice to her little brother (who “would have liked to have had just a little of Gwendolen’s talent”) and has grandiose plans to rule the world, which start with leaving Mrs Sharp behind, and being taken in by Chrestomanci. When the enchanter doesn’t appreciate her talents, Gwendolen becomes increasingly furious, setting in progress a chain of events culminating in a fearsome battle in the castle’s gardens.

Long before Potter, I found joy in the orphan-discovering-they-have-magical-powers trope – and what a moment it is when these powers are finally realised in Charmed Life. There are laugh-out-loud scenes, such as when Gwendolen takes on Chrestomanci’s apparently mild children, Julia and Roger, with a flying slice of bread and marmalade and Julia responds with a levitating jug of cocoa. And the magic Wynne Jones describes is just so fun; imagine using magic to animate your toy soldiers and set them against each other – although Julia’s soldiers always run away. (“‘Because that’s just what I would do,’ Julia said, putting out a knitting needle to mark her place in her book. ‘I can’t think why all soldiers don’t.’”)

Rereading it, I’m delighted by all these moments yet again, but also chortling with pleasure at the inimitable virtuosity of Wynne Jones’s writing, the delicate, understated humour of it all. The way with just a word, she tells us exactly who Gwendolen is. “We are the young Chants,” she tells a station porter “magnificently”. She stares “vengefully” after Chrestomanci. Or: “She had her usual glowing, exultant look, but she was looking secretive and important too.”

And Chrestomanci is just so gloriously vague, often dressed in an impossibly elegant silk dressing gown and looking “like the Emperor of Peru”, always arriving at just the right moment with an arched eyebrow. More than once, my children looked at me perplexed as I shuddered helplessly in mirth at exchanges like:

‘Someone’s been opening my letters,’ said Gwendolen. ‘And I don’t care who it is, but I’m not having it! Do you hear?’ Cat gasped at the way she spoke. Chrestomanci seemed perplexed. ‘How are you not having it?’ he said. ‘I won’t put up with it!’ Gwendolen shouted at him. ‘In future, my letters are going to come to me closed!’ ‘You mean you want me to steam them open and stick them down afterwards?’ Chrestomanci asked doubtfully. ‘It’s more trouble, but I’ll do that if it makes you happier.’

The book is in front of me right now ready to be reread, and once I’m done I’m heading off into the world of The Lives of Christopher Chant and Witch Week for some more Chrestomanci. Then, perhaps, Fire and Hemlock for mystery and romance, or The Time of the Ghost for some proper chills. Diana Wynne Jones: always and forever, my favourite.