I just discovered that my dad owns the first edition of this book (which means that I inherit it) but unfortunately it does not have the cover, so it is not worth all that much. I am tempted to see if I can locate the cover on Ebay, but if I were to do that, the value of the cover will need to increase the value of the book to a point that it will be worth selling (though a quick check on Ebay has indicated that it is not). Of course that is also working on the assumption that the value of first edition Biggles books remains at such a level that it is worth selling.
Anyway, I enjoyed this book but it pretty much read like a Famous Five book that is aimed specifically at boys. In a way there was little difference between your standard Famous Five adventure and this book, and in fact you could pretty much switch the characters around and you would have a Famous Five book. However, it is interesting to note that the Famous Five books are enjoyed by children of both genders, whereas the Biggles books tend to be enjoyed predominantly by boys.
I'll give you a a brief run down of the plot: a Scot who has inherited a lot of money decides that he wants to retire to an island to the North of Scotland which is his family's home, however when he gets there he finds that despite it apparently being deserted, there are people there that do not want him there. However, the only reason that Biggles gets involved is because the Scot hears a plane at night, which means it appears that because there is a plane involved the Special Air Police (this is very much a post World War I novel) can have jurisdiction.
I won't say to much more about it, but I suspect that most people who like the Biggles books may have read this, though when I did a search on Wikipedia to find out the date of the book I discovered that there are actually a huge number of Biggles books out there. My Dad only has a few of them, but I am sure that I will get some more enjoyment from them as I make my way through them. Hey, I may even try a Hardy Boys book one day, despite the fact that they are pretty much a form of cookie-cutter book.