Reading "By Nightfall" (Farrar, Straus and Giroux, 256 pages, $25) by the Pulitzer-winning author of "The Hours" is a lot like witnessing somebody else's midlife crisis; it stirs the same uneasy mixture of fascination and impatience. And whether you end up feeling more fascinated or impatient will largely depend on how much you care about the man at the middle of it all.

Peter, a middle-aged, relatively well-to-do gallery owner and art dealer in New York, is thrown into a state by the arrival of his wife's much younger brother, lovingly referred to as The Mistake, or Mizzy. And Peter, it seems, is quite ready to be thrown. Not altogether happy with his life, his career, his wife or his daughter, he's come to see himself as something of a self-impersonator, though what his true self is remains problematic. He knows he is "impossibly fortunate; frighteningly fortunate." No one, he reminds himself, "has hacked you to death with a machete. But still."

But still.

Mizzy, a lost and troubled young man with a drug habit, appears to Peter as an irresistible incarnation of youth and truth and beauty -- "the person about whom others ask, Who's that?" But just as nothing in this story is what it seems (for instance, "Peter has gotten better over the years at dressing as the man who's impersonating the man he actually is"), Mizzy's allure is fraught with misperception and falsehood.

And once Peter is clear on where his longing has misled him, he sees himself as "a poor, funny little man, isn't he?" In a novel dense with references to film and literature, this moment asks us to see Peter as at one with such archetypes as Hurstwood (in "Sister Carrie") or Emil Jannings (in "The Blue Angel"). But the tragic dimension isn't there. As a professor of mine once said, "Pathos is when you fall off the swing and realize it's not tragedy."

It's not tragedy. It's moving. Much of it is beautifully written. But how it works, and how well it works, will finally be a function of taste.

Ellen Akins is a novelist in Cornucopia, Wis.