The Razor's Edge by Somerset Maugham. From Amazon: “Larry Darrell is a young American in search of the absolute. The progress of his spiritual odyssey involves him with some of Maugham's most brilliant characters - his fiancée Isabel whose choice between love and wealth have lifelong repercussions, and Elliott Templeton, her uncle, a classic expatriate American snob. Maugham himself wanders in and out of the story, to observe his characters struggling with their fates.”