Five Go Down to the Sea (Famous Five)
Enid Blyton died in 1968 but remains one of the best-known and best-loved writers of children's stories.  She is consistently voted a children's favourite in author polls and 1 million of her books are barrowed from libraries every years.  She has over 600 children's books to her credit, including the Famous Five series, the Secret Seven series, the Naughtiest Girl series (all Hodder) and the Malory Towers and St Clare series (both available from Hodder on audio).