This is a tight little book, novella-length really, about a modest, comfort-inclined accountant, Bertram, whose plan for a budget wedding and honeymoon with his fiance, Cary, are thrown up in the air when one of Bertram's firm's owners, nicknamed "Gom" for "Grand Old Man", suggests that Bertram and Cary instead sail to Monte Carlo on his yacht and wed there.
Bertram and Cary take the ride, which takes them out of the element in which they thrived together. They get in over their heads at their hotel and casino in Monte Carlo when Gom fails to show up on time. Bertram, though, develops a "system" and begins to win big in the casino and plots a kind of blindside revenge on Gom.
The whole story is an unhinging of Bertram and his relationship with Cary. The undercurrent is class. Gom's 8th floor office in the clouds, his disdain for Bertram's modest wedding plan and offhanded suggestion of the yacht and Monte Carlo, his failure to show up for the wedding, and the clubbiness among all three of the firm's co-owners all depict a gulf between the Goms of the world and the Bertrams. Bertram's winnings suddenly put him in an advantaged position, but it's also a temptation. And his advantaged position is no more earned or deserved than Gom's birthright was earned or deserved.
The temptation is to see it all as a story of "money can't buy happiness." But there's always more to it than that with Graham Greene.
This isn't one of my favorite Greene books. He called some of his books "entertainments". I'd put this one in that class. I enjoyed reading it, it made me think, but it's not The Power and the Glory, or even The Comedians.