Found amongst my Dad's old books, The African Queen by C S Forester. This is probably more well known as the 1951 John Houston film starring Humphrey Bogart and Katherine Hepburn but it was a book long before that, first published in 1935. The film is pretty good and Bogart won an Oscar for his part in it although, of course, Hollywood changed various parts of the plot to simplify matters and over-dramatise the ending, losing some of the subtleties in the process.
C S Forester subsequently wrote the Hornblower series of books, all of which I have read at some time and can highly recommend (see The C S Forester Society). Forester shows the same knack in The African Queen of combining an adventure story with a narrative describing how the characters change and develop as events act upon them. Very enjoyable, and there's no waffling. Note: in the book the woman is the stronger character and takes the lead but in the film the man is more heroic.