Released with Faber's "biggest trade campaign ever", the novel received largely positive reviews from critics, who particularly praised its treatment of grief and family relationships.

While some critics found aspects of the novel's tone precious or its gender dynamics problematic, most viewed it as a successful evolution of Rooney's literary style, with several considering it her most mature and philosophically ambitious work to date.

However, Peter still harbors unresolved feelings for his close friend and ex-girlfriend Sylvia, a 32-year-old English professor, whose chronic pain following a car accident ended their relationship.

[3] The novel was influenced by James Joyce's Ulysses, with Rooney describing Intermezzo as partly emerging from her reading of that book and her sense that it "demanded a response".

The novel explores how the death of a father affects two brothers differently, examining the ways grief can divide and unite family members.

[11][9][12] This extends to questions of gender roles and economic influences on romantic relationships, while also addressing the gap between ideological beliefs and personal behavior.

[6] The sibling relationship at the novel's center serves as a lens through which these power dynamics are explored, particularly how family bonds both constrain and enable personal growth.

[16][12] Critics noted that Peter's stream-of-consciousness passages particularly represent a stylistic experiment for Rooney, with shortened sentences and fewer verbs creating a choppier but rhythmically consistent flow reminiscent of writers like Eimear McBride and Samuel Beckett.

[9] While the novel retains Rooney's practice of omitting quotation marks and approximating modernist techniques,[16] it is her most stylistically varied work.

[5] Rooney's characteristic style, often "mischaracterized" as "blank" or "flat", maintains its televisual qualities in Intermezzo, with seamless sentences, snappy dialogue, and chapters that conclude like complete episodes.

[17] In the United States, 140 bookstores hosted release parties for the novel, a scale of promotion typically reserved for young adult blockbuster series.

[21] Alexandra Harris in The Guardian called the novel "an accomplished continuation of the writing that made Rooney a global phenomenon" while noting it was "more philosophically ambitious, stylistically varied, disturbing at times and altogether stranger".

Johanna Thomas-Corr in The Sunday Times praised how "the explosive arguments between Peter and Ivan, in which one knee-jerk judgment breaks the fall of another, are among the most masterly scenes she has written.

"[15] B. D. McClay in The Wall Street Journal noted that the brothers are "aware that they play some sort of mysterious central role in another person's life and development, whether they want to or not.

"[13] Cal Revely-Calder in The Telegraph observed that "Peter, whose chapters supposedly parallel Ivan's but soon accrue greater force, is Rooney's finest portrait of a tortured man since Connell Waldron.

James Marriott in The Times argued that "the novel's insistence on a mood of ethical and intellectual refinement can feel claustrophobic and precious.

In Vulture, Andrea Long Chu analyzed how the novel suggests that "love is real precisely because it is a product, one created by social conventions, by market forces, by systems of violence.

"[11] Claire Lowdon in The Spectator called the book "simple, heart-warming moral tales full of sex", while noting that it "left me feeling I might have a stab at being a better person".

[16] In New Statesman, Lola Seaton wrote that while "Intermezzo lacks the taut self-assurance of Conversations with Friends and Normal People", it represents "an honourable, tenacious and not unsuccessful attempt to go beyond them.