Sally Rooney's "Normal People" was a masterful depiction of first love. Readers of the Irish author's second novel — and, later, viewers of the acclaimed Hulu series — followed Marianne and Connell coming together and coming undone over the course of four years. Their chemistry was so special that the book's title seemed to apply to others. "I did used to think I could read your mind at times," said Connell. "But maybe that's normal." "It's not," Marianne assured him.

In her latest novel, "Beautiful World, Where Are You," Rooney turns her attention once again to romantic entanglements. This time, instead of putting one Irish couple under the spotlight, she reprises the structure of her debut, "Conversations With Friends," and examines the dynamics of two pairings. She also extends her gaze beyond sexual relations to explore the occasionally fraught yet ultimately unbreakable friendship between her two female leads.

These women power the novel. Alice is a 29-year-old writer from Dublin whose books have made her wealthy and famous. However, success has not brought her happiness: She was admitted to a psychiatric hospital after suffering a nervous breakdown and now lives alone on the west coast of Ireland.

Her best friend Eileen is an editorial assistant on a literary magazine in Dublin and struggles to make ends meet. Like Alice, she experiences low moments where she feels like a failure: "It's so hard to see the point sometimes, when the things in life I think are meaningful turn out to mean nothing, and the people who are supposed to love me don't."

Alice attempts to assuage her loneliness by hooking up with Felix through a dating app. Eileen rekindles a spark with childhood friend Simon. Felix works in a shipping warehouse and is prone to getting blindingly drunk; Simon is a senior political adviser and a committed Catholic. After a series of meetups and fallouts, all four gather at Alice's huge rectory by the sea. There they test the limits of the forces that bind them.

"Beautiful World, Where Are You" is something of a mixed bag. Even if opposites do attract, it is hard to fully believe in Alice and Felix's blossoming love. Their first date is disastrous. Undaunted, Alice then invites Felix, still a virtual stranger, to accompany her on a promotional trip to Rome. He finds her "weird" and condescending and treats her appallingly. He describes himself as "not the most reliable character going." And yet still this emotionally damaged woman considers him someone worth pursuing.

Rooney also taxes us with the rambling e-mails Alice and Eileen send one another — correspondence that covers a range of topics from politics to plastic, class conflict to early writing systems.

Her narrative becomes engaging when her characters swap self-absorption for interaction. We may have to surrender disbelief in places, but otherwise we marvel as Rooney continues to write convincingly and captivatingly about human relationships in all their relatable complexity.

Malcolm Forbes has written for the Times Literary Supplement, the Economist and the New Republic. He lives in Edinburgh, Scotland.

Beautiful World, Where Are You
By: Sally Rooney.
Publisher: Farrar, Straus & Giroux, 368 pages, $28.