The Rabbit Listened
Cori Doerrfeld
Not about death in particular. About what a child needs when something has fallen apart.
Children's books about grief, loss and very big feelings
These are for hard weeks. Read them yourself first, because you will want to know what is coming, and because each one handles loss differently.
The Invisible String
Patrice Karst
Comfort for separation or death. It mentions heaven, so read it first.
Charlotte's Web
E.B. White & Garth Williams
The honest long version, for older kids. Death is real here, and so is what comes after it.
Where the Wild Things Are
Maurice Sendak
For the rage that turns up in grief and surprises everybody.