Author: John CurranAgatha Christie's Complete Secret Notebooks brings together for the first time Secret Notebooks and Murder in the Making, two volumes that explore the fascinating contents of her 73 notebooks. This includes illustrations, deleted extracts, unused ideas, two unpublished Poirot stories and a lost Miss Marple. When Agatha Christie died in 1976, aged 85, she had become the world's most popular author. With sales of more than two billion copies worldwide in more than 100 countries,…