Although I’ve written a series of books for children who are ill, life-limited or grieving, I don’t know of a book specifically about a child whose parent is chronically ill.My recommendation would be to use quality story books to explore the topic through feelings and questions.
I would recommend books you can both enjoy together which talk about emotions together because empathising with characters in stories helps us process our emotions too.
One I love is The Paper Dolls by Julia Donaldson. It’s a good one for talking about loss, including loss of freedom and the others losses you and he will have suffered this year. It’s in this bundle of Julia goodies although I’m sure you could get it on its own here.
I also like The Emotionary, expensive but a beautiful hard back book we go back to time and time again when processing difficult emotions. Rachel Turner from Parenting for Faith recommended it to me and I’ve found it a really helpful one. (She’s brilliant at helping children develop their EQ!)
I think I would still recommend the book: Jesus still loves Joe – as it looks at all the different emotions we feel in grief and reaffirms that we are still loved. It usually makes adults cry, so maybe read it on your own first 
What book ideas would you add?