We Didn't Mean to Go to Sea by Arthur Ransome: Book #5 for 2017
The seventh book in the Swallows and Amazons series focuses solely on the Swallows (John, Susan, Titty and Roger), although Nancy, Peggy, Dick and Dorothea are all mentioned briefly.
The story opens with the Swallows taking another boat trip, supervised by a sea captain called Jim, to make sure they don't sail out of the harbour. Of course, the title is an obvious clue to what is going to happen...
Jim has to sail to shore to get supplies, and he never returns (his apparent disappearance is explained later in the book), and the boat is somehow swept out to sea with the kids on board; the storyline provides the greatest amount of peril yet in the series, and mostly revolves around the Swallows attempting to steer the ship back to land on stormy waters. During the story, there are also a few references to their absentee father, which will of course become relevant later on.
I noticed this was the first book to have chapters told from the point of view of the secondary characters, with one episode revolving around their mother and younger sister Bridget (I think Bridget has her first speaking lines in this book) as they wonder where the kids have got to, unaware of the trouble they are in.
Overall, despite the absence of Nancy and Peggy, who I always found to be some of the more entertaining characters, I quite enjoyed this book, and towards the end it started feeling like nothing that I'd read so far in the Swallows and Amazons novels. I have the next book, Secret Water on my shelves and intend to read it very soon.