The book is
Wheelbarrows At Dawn, by Angie Gardner and Neil Holford, a biography of Hilary Tolkien which discusses the relationship of the two brothers. It was so close to publication that a launch party was planned for December 4th.
But apparently one cannot discuss JRR Tolkien in a book about his brother Hilary.
Publisher's announcement of cancellation of publication
Perhaps soon we will hear that one cannot discuss JRR in a book on C.S. Lewis.
I haven't gone looking for any comments from the Estate.
What this bodes for Tolkien scholarship boggles the mind.