Swallows and Amazons is Arthur Ransome's first book in the Swallows and Amazons series. It is not his best but it certainly sets the stage for all the others and so shouldn't be missed. Please don't be discouraged by that statement; Ransome is an exceptional author and if you're looking for a book about children sailing for a child (8-16 comes to mind), I cannot recommend anything more highly. It's simply that Ransome is still working on his form in this book and what passes as "not his best" far exceeds that of many, many other authors.
Put another way, this is a great book and very well-written; his subsequent ones are even better! Here's a brief synopsis:
A quartet of children (plus Mom, baby and nurse; Dad's away at war) arrives at a lake in England's Lake District for summer holiday. They spy this glorious island, just begging to be discovered. It turns out they already have a beautiful boat, Swallow and the oldest already knows a fair amount about sailing. They obtain permission to sail to and camp on the island and the adventures begin. Turns out the children who crew Amazon lay claim to this island. Throw in a retired pirate, some friendly natives, some very detailed descriptions and explanations of sailing and you've got a fine story with an excellent setting, some terrific characters and a wild ride as the Swallows and Amazons spend their summer holiday.
So wonderful, in fact, that they don't want it to end. Toward the end of the book, Mrs. Dixon (a friendly native) suggests:
". . . But perhaps you'll be coming again next year."
"Every year. For ever and ever," said Titty.
"Aye," said Mrs. Dixon, "we all think that when we're young."
Indeed, I wanted the book to go on, "for ever and ever". The series doesn't go on for ever but there are others and they are even more delightful.
If you'd like additional information on Arthur Ransome's Swallows and Amazons, check out The Arthur Ransome Society home page.