Swallows and Amazons paperback 1999
First published 1985. Known in the U.S. as "trade paperbacks", these volumes are as large as the hardback editions. Still available in the U.S.
1999 price $14.95
The title pages include the "Author's Note" claiming that the Swallows and Amazons story came solely from Ransome's own childhood. Full details of the first edition here.