The Fault in Our Stars received critical acclaim. Critics mostly praised the book for its humor, strong characters, language, themes and new perspective on cancer and romance. The New York Times ' review of the book called it "a blend of melancholy, sweet, philosophical and funny" and said that it "stays the course of tragic realism", while noting that the book's unpleasant plot details "do nothing to diminish the romance; in Green's hands, they only make it more moving." NPR's Rachel Syme noted that "[Green's] voice is so compulsively readable that it defies categorization," saying that the "elegantly plotted" book "may be his best."  Time called The Fault in Our Stars "damn near genius." Entertainment Weekly wrote, "[Augustus and Hazel's] love story is as real as it is doomed, and the gut-busting laughs that come early in the novel make the luminous final pages all the more heartbreaking", and gave the novel an overall A− grade. Amazon.com calls it "insightful, bold, irreverent, and raw" and Green's "most ambitious and heartbreaking work yet." The Manila Bulletin says that the book is "a collection of maudlin scenes and trite observations about the fragility of life and the wisdom of dying. And while it does talk about those things and more, the treatment of it is far from being maudlin or trite." The Manila Bulletin also added that "Just two paragraphs into the work, and he immediately wallops the readers with such an insightful observation delivered in such an unsentimental way that its hard not to shake your head in admiration." The Manila Bulletin stated that The Fault in Our Stars was a triumph for John Green. USA Today called it a "elegiac comedy." They gave the book a rating of four out of four stars.The School Library Journal stated that it was "a strong choice for Adult Collections." The Fault in Our Stars received a starred review from Kirkus Reviews, who described it as "a smartly crafted intellectual explosion of a romance."
Several well-known authors have contributed their own positive reviews for the book. Jodi Picoult, author of My Sister's Keeper, calls The Fault in Our Stars "an electric portrait of young people who learn to live life with one foot in the grave." She goes on to say that the novel is "filled with staccato bursts of humor and tragedy." Bestselling author of The Book Thief, Markus Zusak, describes it as "a novel of life and death and the people caught in between" and "John Green at his best". Pertaining to Green's writing throughout the book, E. Lockhart, author of The Boyfriend List, says "He makes me laugh and gasp at the beauty of a sentence or the twist of a tale. He is one of the best writers alive and I am seething with envy of his talent." Time named The Fault in Our Stars as the #1 fiction book of 2012. Kirkus Reviews listed it among the top 100 children's books of 2012. It also made USA Today 's list of the top 10 books of 2012. In 2013, the Edmonton Journal named the book one of their "favourite books of the year."
One notable unfavorable opinion appeared in the Daily Mail. In the piece, the plot of The Fault in Our Stars was described as "mawkish at best, exploitative at worst" and the book was characterized as belonging to the "sick-lit" young adult genre, together with other young-adult novels such as Never Eighteen and Before I Die. This entire genre, as well as the genre of young-adult novels dealing with suicide and self-harm (the piece mentions Thirteen Reasons Why, By the Time You Read This, I'll Be Dead, The Lovely Bones, and Red Tears) was criticized as being "distasteful" and inappropriate for their target audience of teens. The Guardian criticized the piece, pointing out in particular that The Fault in Our Stars was chosen by The Guardian as that month's "teen book club choice" because "it's a gripping read, featuring two compelling characters, that deals sensitively and even humorously with a difficult situation without descending into mawkishness." In general, The Guardian faulted the Daily Mail for suggesting that the issues of illness, depression, and sexuality are inappropriate precisely "in the one place where difficult subjects have traditionally been most sensitively explored for teens: fiction written specifically for them." For his part, in an interview for The Guardian, John Green said: "The thing that bothered me about The Daily Mail piece was that it was a bit condescending to teenagers. I'm tired of adults telling teenagers that they aren't smart, that they can't read critically, that they aren't thoughtful, and I feel like that article made those arguments."