Talented Mr. Ripley by Patricia Highsmith
Tom Ripley is chosen by the wealthy Herbert Greenleaf to retrieve Greenleaf's son, Dickie, from his overlong sojourn in Italy. Dickie, it seems, is held captive both by the Mediterranean climate and the attractions of his female companion, but Mr. Greenleaf needs him back in New York to help with the family business. With an allowance and a new purpose, Tom leaves behind his dismal city apartment to begin his career as a return escort. But Tom, too, is captivated by Italy. He is also taken with the life and looks of Dickie Greenleaf. He insinuates himself into Dickie's world and soon finds that his passion for a lifestyle of wealth and sophistication transcends moral compunction. Tom will become Dickie Greenleaf--at all costs.

Very interesting. I thought I had read it many years ago but now I'm not sure I did.