Jacob and Julia are aware of their good fortune. Shopping with a client in a bespoke hardware store, Julia thinks: “It was elegant, and it was obnoxious, and in a world where the bodies of Syrian children washed up on beaches, it was unethical, or at least vulgar.”

This life is coming unstitched at the seams. Julia finds erotic texts, sent to another woman, on Jacob’s cellphone. An already distant marriage becomes a fractured one. “Here I Am” chronicles their slow and traumatic separation, one that some readers will search through for resonances with Mr. Foer’s own much-publicized divorce from the novelist Nicole Krauss.

Jacob and Julia’s insults fly freely; so do everyone’s. Mr. Foer’s dialogue is so crisp you can imagine him writing for the stage. When Jacob tells Julia he is going to Israel to fight, she responds, “What, write for the army paper?” Jacob’s unreconstructed intellectual tank of a father declares about the Arab world, “At the end of the day, we love kung pao chicken and they love death,” and about mohels, “If God had wanted us to be uncircumcised, he wouldn’t have invented smegma.” Even the jokes in “Here I Am” land. An example:

“You know what Lou Gehrig’s final words were, right?”

“I don’t want to die?”

“Damn, Lou Gehrig’s disease, I should have seen that coming.”

“Here I Am” at its best is a reminder that, as Mr. Roth once put it, “It isn’t what it’s talking about that makes a book Jewish — it’s that the book won’t shut up.”

In “Here I Am” (the title comes from Abraham’s response after God called out to him) Mr. Foer’s great subject is loss, and he examines it from many angles. About his sons, Jacob thinks: “No baby knows when the nipple is pulled from his mouth for the last time. No child knows when he last calls his mother ‘Mama.’ No small boy knows when the book has closed on the last bedtime story that will ever be read to him. No boy knows when the water drains from the last bath he will ever take with his brother.”

A different sense of loss comes over you while reading the final sections of “Here I Am,” a sense that arrives with an awareness that this vigorous novel amounts to less than the sum of its parts. This book offers intensities on every page. Once put down it begs, like a puppy, to be picked back up.

But its insistent winsomeness cloys. Characters begin to make comments that sound like insults directed at the novel itself: “Life isn’t a Wes Anderson movie”; “If I were you, I’d tone down the intelligence”; “You’re an adult, Mark, not a Shel Silverstein character contemplating emotional boo-boos on the stump of a tree whose trunk he used for a dacha, or whatever.”

“Here I Am” has more teeming life in it than several hundred well-meaning and well-reviewed books of midlist fiction put together. That Mr. Foer can be so good makes us hold him to a higher standard, and demand from him something closer to greatness.