A young boy lives in a tower block in a near future wasteland. There is a strange lady who pushes around a trolley with a diamond encrusted tortoise in it. She was a writer and she wrote a book (the manuscript is also in the trolley?). There is a newspaper magnate involved somehow.
This is definitely “Dakota of the White Flats” by Philip Ridley (illustrated, in the British edition, by Chris Riddell – I think it was the first time I’d seen his highly characteristic illustrations).
Dakota is actually a girl (and she has a sidekick, also a girl, called Treacle). She lives with her mother, Lucy, who is agoraphobic after being left by Dakota’s father and spends all her time in an armchair, the Cocoon of Comfort. There is indeed a diamond-encrusted tortoise and the lady with the trolley, Medusa, is a ghostwriter for the millionaire bestseller Lassiter Peach who is – sort of – the villain of the piece.
It’s all wonderfully weird.
Wow.
It occurred to me later that it’s not the Cocoon of Comfort, it’s the Cocoon on Castors. (Doh!)