Reviewed by Linda C. Brinson WE MUST BE BRAVE. By Frances Liardet. Penguin Audio. Read by Jayne Entwistle and Juliet Mills. 16 hours; 13 CDs. $66. Also available in print from G. P. Putnam’s Sons. This beautiful, moving novel is the first to be published in America by Frances Liardet, a British writer and translator,…