All ratings relative to the genre, of course.
Ambler wrote a series of novels from 1936-1940, then stopped for 12 years, returning to fiction in 1952. This is the last of the early works. Though these early works are considered "Classics", I found this book a shade immature in its technique, compared (at least) to Passage of Arms, which is truly brilliant. The lead character, Graham, is foolish (in a very British way), and so not wholly believable. Because of this, the plot (which hinges on this character) suffers somewhat. But the secondary characters are vivid and, in some cases, compelling. And the finale compensates for any flaws leading up to it. An excellent book for Ambler fans, but not necessarily the best starter book.