Idle Talk: Letters 1960–1964 by Gwen Harwood Brandl & Schlesinger, 2015, 181 pages, $29.95 ____________________________________   It is not uncommon for writers to have their correspondence published after their demise, but the late Gwen Harwood had a collection of her early letters printed under the title Blessed City (1990) while she was still alive. Assembled by Alison Hoddinott, this series of letters written during the Second World War and addressed to the then Gwen Foster’s friend Tony Riddell amounted to an autobiography in disguise, which is how it was classified by the marketing department of Angus & Robertson, the publisher.…