Sweet Sorrow has received positive reviews from critics, who noted Nicholls's skill in evoking the nostalgia and intensity of first love, his ability to balance humour and heartfelt emotion, and his storytelling.

He lives with his depressed, unemployed, and alcoholic father and feels directionless and uncertain about his future, having failed his GCSEs and facing a long, empty summer before the results come out.

Fran goes off to college, full of excitement and ambition for what lies ahead, while Charlie wallows in self-pity and uses the excuse of looking after his depressed father to avoid moving forward with his own life, taking a job working at an airport lounge.

[5][3][7] The novel explores the challenges and uncertainties that often accompany the transition from adolescence to adulthood, including the struggle to establish one's identity, navigate complex relationships, and find a sense of belonging.

Writing for The Guardian, Alex Preston lauded the novel as "a book that does what Nicholls does best, sinking the reader deep into a nostalgic memory-scape, pinning the narrative to a love story that manages to be moving without ever tipping over into sentimentality, all of it composed with deftness, intelligence and, most importantly, humour".

[2] Holly Williams of The Independent awarded the novel 4 out of 5 stars, describing it as "an ideal blend of the gently humorous and utterly heartfelt" and "a thrummingly intense evocation of both a first high and first love".

[3] In her review for The Washington Post, Bethanne Patrick commended Nicholls's "acute understanding of those moments in life that change things" and his ability to remind readers that "we've all had our own sweet sorrows, first loves that, when recounted, might set other people's teeth on edge".

[4] Stuart Kelly of The Scotsman praised the novel's tragicomic nature, stating that "Sweet Sorrow manages to be interesting, moving, hilarious and sad at the same time" and that "sentimentality is an underrated genre in some ways.

[6] Library Journal's Barbara Hoffert highly recommended the book, writing, "As Charlie notes, displaying a growing understanding of Shakespeare, Romeo and Juliet '[is] stuffed with anticipation,' and readers will be, too, as Nicholls masterfully unfolds events.