It is due out this month from Knopf. Publisher's Weekly gave it a starred review. As well as School Library Journal. And my mother gave it four stars. It hasn't been reviewed by us yet.
Most libraries subscribe and keep their current copy in the children's room.
I am a student teacher researching for an essay about Roald Dahl. I was delighted to find the letter and information about Laura Ingalls Wilder and will visit your web site again.