Upon beginning Liz Moore’s engaging, quirky novel “Heft,” it’s a relief to see that the teenager inadvertently romancing her professor is not a hip, wiser-than-her-years cliché. Charlene Turner is awkward, her bangs sprayed upright in a style that is not “in,” even in the ’80s. She doesn’t understand literature, discussing characters as if they are friends she disapproves of. Urged to consider the meaning behind a Greek tragedy, she writes a paper insisting that Medea was selfish: “She shouldn’t have killed her children. She should have killed herself.”

That moment is recalled 20 years later by her professor, Arthur Opp, who remains charmed and more than a little in love with Charlene despite how briefly they were friends. He now weighs some 550 pounds, never leaves his house in Brooklyn and sees no one but the delivery people from Amazon or, more frequently, the upscale food purveyors Harry and David. I wouldn’t recommend reading “Heft” while you’re on a diet. The book, while depicting Arthur’s shame, is not afraid to convey his joy of food.

His connection with Charlene – based mainly on recognizing that she is someone, like him, who doesn’t fit in – remains the highlight of his life, although it ended his teaching career. When she calls after decades of a pen-pal correspondence, Arthur looks at his heft, his mess of a house, his lack of friends, and compares them with all the lies he’s been telling Charlene. He decides he must make some changes before meeting her again.

Arthur’s voice is engaging. His honesty is funny, even if the revelations of his haplessness are painful. He doesn’t know what to make of the photograph Charlene sends him of her teenage son he hadn’t known about. He prepares for her visit even while he avoids phoning her, hanging up when he gets the answering machine.

When the story moves to Charlene’s world, it is her son, Kel, who takes over. He lives with his mother in a rough part of Yonkers, but Charlene has gotten a job at the affluent Pells Landing High School so that Kel can attend.

His embarrassment at having an odd, increasingly troubled mother whom he loves is sharply and movingly depicted. The divide between his home life and the wealth at Pells Landing makes for a nuanced portrait of class. For all his deftness at making friends, Kel is another fish out of water.

When an act of desperation leaves both Kel and Arthur stranded, the book reveals its true strength. Without archness or overly artistic sentences, “Heft” achieves real poignancy. The author’s explanation of Arthur’s psychology is perhaps too neat, but the warmth, the humanity and the hope in this novel make it compelling and pleasurable.