| Very few things scare Amazon Pirate First Mate Peggie Blackett -- mostly thunder, but also her older sister, Nancy, and the Great Aunt.
The only thing that scares Amazon Pirate Captain Nancy Blackett (well, "Ruth", properly, but Amazon Pirates are ruthless) is the Great Aunt.
Great Aunt Maria Turner, who raised Nancy & Peggie's widowed Mother and their Uncle Jim, is a formidable maiden lady of firm opinion, unbending will and repressive manner. "Having fun" is not on her list of summer tasks that well-brought-up children need to perform during the Summer Holidays. And dressing in comfortable shorts, knit shirts and red stocking caps is hardly suitable for Young Ladies in their early teens. (This is, after all, the 1930's)
Not that this is particularly worrisome in the normal frame of things, because she lives Far Away.
But somehow Aunt Maria gets word that Ruth and Margaret are to be alone for a goodly part of the Summer Holidays as Captain Flint (Uncle Jim) takes their mother on a cruise for her health... and decides to visit Beckfoot for most of that period and make sure that Nancy and Peggie don't get into trouble. (This puts the lady's opinion of her own abilities on a par with King Canute's...)
Not that this, even so, would be worse than Unpleasant... except that their friends, Dick & Dorothea Callum ("the D's") are to be staying at Beckfoot... and it's a sure bet that the Great Aunt would visit a devastating scold on their Mother if she found out that they were having other guests their own age to stay, to be supervised only by Cook.
And so, quicker than you can say "Are you sure this isn't a Bad Idea?" Dick and Dorothea, city kids with limited experience at camping and fending for themselves, wind up ensconced for the length of the GA's visit in "the Dog's Home" -- a one-room stone forester's hut in the woods up above the lake.
And, since a number of people know that they're supposed to be at Beckfoot, and don't know it's a secret, and because Dick is supposed to be working with Captain Flint's friend on Captain Flint's houseboat on some chemical analysis of samples from a mine they discovered in the previous book and because Murphy's Law applies to everything in life, from there the story becomes more and more complex and full of hair's-breadth escapes and humourous adventures and close calls (the burglary at Beckfoot being particularly fun).
In the end, of course, all is (relatively) well, the GA gone, the D's have their own boat to race with "Swallow" and "Amazon" and the Swallows are due to arrive any day and most of the Summer still stretches ahead.
Like all the rest of the series, humourous adventure fiction for the YA age group. (And perhaps a bit younger; since they were mostly written for British juvenile audiences, and sixty to seventy years ago to boot, the "Swallows & Amazons" books may contain references and language that today's younger readers may have some problems with. OTOH, i first read "Swallows & Amazons" [the first book] at age eight or nine and i had no problem with it.)
Which is not to say that adults can't enjoy them -- many do. Buy them for a son, daughter, nephew or niece and give them a try before you pass them on; Ransome has a huge adult readership worldwide, even today.
(The cover shown above is from the 1971 Puffin (U.K.) paperback edition; it's the only one i could find online)