Set in the 1980s in West Germany, the story follows 16-year-old Frieder Büchner as he spends a transformative summer with his grandparents, with themes of first love, friendship, and family relationships.

After failing his ninth-grade year and needing to retake exams in Math and Latin, Frieder is sent to stay with his grandmother Nana and step-grandfather Walter, a strict medical professor, for six weeks to ensure he studies.

Frieder discovers and secretly reads his grandmother's diaries, learning about his grandparents' post-war love story, and sees his own feelings for Beate reflected in these accounts.

While the protagonist Frieder is not a direct representation of Arenz, the character benefits from the author's adolescent experiences, including academic struggles and the impact of loss.

The review highlighted the "generosity and joy" in Arenz's writing, calling it "very rare in modern fiction" and praising the novel's "understated and empathetic examination of a collection of characters.

"[2] Christoph Schröder, writing for Deutschlandfunk, praised Arenz's "good sense for the summer-heated city atmosphere" and "the mood of the sluggish 1980s in West Germany."

He further criticized the novel's occasional lapses into banality when including general reflections, and described the ending as "a somewhat sweet resolution in a dramaturgically simple circular conclusion.

"[3] Dirk Kruse from Bayerischer Rundfunk praised the novel as "exciting and poetic," noting Arenz's great empathy for young people and his ability to create vivid characters.

[1] Anne Smuda from Thüringische Landeszeitung praised the novel for its vivid portrayal of youth, change, and love in the 1980s, describing it as "a must-have for late summer evenings.

Pollerhof highlighted Arenz's ability to convey these themes in a way that feels genuine and not overly sentimental, calling it "the good kind of kitsch" that is easily forgiven for its emotional resonance.

Pfanner compared the novel's literary quality to works like Siegfried Lenz's The German Lesson and Friedrich Torberg's Young Gerber [de], suggesting it could be suitable for school curricula.

"[5] In the UK, One Grand Summer was recommended as a holiday read by Saga magazine, which described it as "funny, touching, troubling, with the growing bond between Frieder and the Professor at its heart.