The daughter of eccentric aristocrats marries a Wall Street tycoon of dubious ethics during the Roaring Twenties. That sounds like a plot that F. Scott Fitzgerald might have written, or Edith Wharton. But “Trust,” by the writer Hernan Diaz, is very much of our time. The novel is told by four people in four different formats, which offer conflicting accounts of the couple’s life, the tycoon Andrew Bevel’s misdeeds, and his role in the crash of 1929. And though a book like “The Great Gatsby” tends to skirt around the question of how the rich make their money, Hernan Diaz puts that question at the heart of “Trust.” “What I was interested in, and this is why I chose finance capital, I wanted a realm of pure abstraction,” he tells David Remnick. Diaz was nearly unknown when “Trust,” his second novel, won the Pulitzer Prize this year.