All joking aside, this is a well-plotted and engaging romantic story, which works on multiple themes. There is the 'coming out' narrative mixed with travel, the 'love under pressure' theme, and the suspense and fear of being compromised. Highsmith is an uncanny writer when it comes to describing human behavior - in personal tics or conversation or gesture. 
 Sixty years after, this genre needs more happy endings. This is a story that lives and breathes.