What I like most about Shute's novels is that he (always) makes me care about his characters. In this case the story feels plausible or possible, even if really rather unlikely (see the author's note below). It being one of his earliest novels, set in about 1926, i.e. almost 100 years ago now, the social setting, manners, and period detail is also very interesting for me. I enjoyed the story, which kept me interested to the end, and there's also a lovely little two page digression in there about how worried a war-pilot who learned to fly in 1916 might have been about unwittingly causing a fatal spin by poor execution of a turn.
BTW, I read the Pan 1966 edition, although the cover is different to the one shown here, it has the ISBN number and cover image (in which you can clearly see the Pan emblem in the top left) of the edition marked as Macmillan 1969 in Goodreads. I wouldn't normally care, but this particular edition has quite a good author's note at the front (dated 1951), which I've reproduced below, as it says something interesting of what Shute's own later opinion of this book was:
"This was the second of my books to be published, twenty-three years ago. It took me nearly three years to write, because I was working as an engineer on the construction of an airship and I wrote only in the evenings in the intervals of more important technical work. It was written through from start to finish twice, and some of it three times.
Clearly, I was still obsessed with standard subjects as a source of drama - spying, detection, and murder, so seldom encountered by real people in real life. Perhaps I was beginning to break loose from these constraints: the reader must judge that for himself.
In revising the book for re-issue I have altered half a dozen outmoded pieces of slang, but I have made no other changes. The book achieved publication in the United States under the somewhat uninspiring title 'The Mysterious Aviator'."