Patrick Ness's novel (based on an idea by Siobahn Dowd) has been made into a stage play, directed by Sally Cookson.
The play is going to be showing at the Old Vic in London, from 7th July to 25th Aug, but first, it's at the Old Vic in Bristol, and I went to see the 2nd performance, on 1st June.
I wasn't sure what to expect - the set is very sparse, other than the Yew Tree (made from ropes, woven afresh each time it is needed), and the ensemble plan multiple roles, from Conor's schoolmates, nursing staff, kings and people in the Monster's tales.
It has moments of lightness and humour, and is particularly poignant as Conor tries to hold on to his belief that his mother will get well, and as his reactions to her illness - fighting with a school bully, and smashing up a room at his grandmother's house, and the refusal of his teacher and grandmother to punish him, "What would possibly be the point?", his teacher asks.
The culmination of the play, as Conor is forced to tell his own tale, and explain his own nightmare, had me in tears.
This is a very powerful production, and Matthew Tennyson (Conor), Marriane Oldham (Mum) and Stuart Goodwin (the Monster) were particularly good.
See it, if you can. It is at Bristol Old Vic until 16th June, and then at the Old Vic in London from 7th July.