“I’m not a bad guy,” is the first thing Yunior, Junot Díaz’s favorite protagonist, tells us about himself in Díaz’s latest book. The statement is precisely the sort of dissembling lie a disreputable man would tell. Is it the truth or merely a hope to which the increasingly desperate Yunior clings?

Díaz, who has lived with Yunior and his idiosyncrasies for so long — three books and many headaches and heartaches now — agrees that the answer is complicated.

“He’s so difficult,” Díaz says. “He’s just so difficult! There’s something knotted about him. But he’s human in his vulnerability; he’s human in his awfulness. He’s human in his struggle for something better than his life, even in his stubborn unwillingness to head in the direction of his better self.”

Díaz, who will talk about Yunior and This is How You Lose Her (Riverhead, $26.95) Monday at Miami Book Fair International, first introduced Yunior in his acclaimed short story collection Drown. Eleven years later, Yunior reappeared to narrate the magnetic novel The Brief Wondrous Life of Oscar Wao, which blended savage Dominican history with geek culture, earned Díaz a National Book Critics Circle Award and a Pulitzer Prize and almost certainly contributed to Díaz’s receiving of a MacArthur “genius” grant.

Now Yunior has returned in a second collection of linked stories about love and loss. In them Yunior, whose family has emigrated from the Dominican Republic to New Jersey, faces his father’s abandonment, his older brother’s death from cancer, his own thoughtless betrayal of women and fear for the future. He breaks hearts. He gets his own broken. He writes: “This is what I know: People’s hopes go on forever.”

What is it about this guy that draws Díaz back to him?

“I knew immediately after Drown I wanted to write this crazy story about a Dominican cheater,” Díaz says, adding that he started the new book immediately on the heels of Drown. In the meantime, Oscar Wao intervened. “It took forever. I didn’t think this book was moving forward. It took years for each story to come together. It was kind of a wild thing. I wasn’t expecting it to take this long, honestly.”

Yunior is a cheater; in the book’s opening story, The Sun, the Moon, the Stars, he’s scrambling to keep his girlfriend from leaving him after she learns of his infidelity (“I cheated on her with this chick who had tons of eighties freestyle hair. Didn’t tell Magda about it, either. You know how it is. A smelly bone like that, better off buried in the backyard of your life. Magda only found out because homegirl wrote her a f------ letter.”) He’s crushed when Magda leaves him, yet continues to pursue his sucias, sabotaging his relationships.

Díaz has taken some heat from critics for what they perceive as misogyny in the stories, but Miami author Edwidge Danticat says Yunior’s confessions have the ring of truth.

“You feel as though the character is speaking directly to you,” she says. “I think if you grow up in a certain environment in the DR or in immigrant New York or poor in New Jersey, you recognize these characters. They feel familiar to you, even though he brings a different light to them. I know he’s been criticized for some of the raw honesty of the characters, especially the male characters. I know him well enough, and I feel like as a reader and a friend I understand the project he’s engaged in as a man. ... He couldn’t be more feminist-minded in what he does.