In School Library Journal, Jane Abramson commented that the book was "stylistically superb" and that it "packs a punch that will leave readers of any age reeling." A Publishers Weekly reviewer wrote, "Ms. Hinton is a brilliant novelist," and Margery Fisher, in Growing Point, noted, "Once more in the American urban scene is a book as uncompromising in its view of life as it is disciplined." She also wrote, "Of the three striking books by this young author, Rumble Fish seems the most carefully structured and the most probing." Jay Daly wrote in Presenting S. E. Hinton, "In the end we respond to Rumble Fish in a much deeper way than we do to [her previous book] That Was Then, This Is Now. It's an emotional, almost a physical response, as opposed to the more rational, intellectual reaction that the other book prompted." He also commented that the book "works as a novel.... And there is a name usually given to this kind of success. It is called art."

However, not all critics agreed that the book was superb. In the Nation, Michael Malon remarked that he found it difficult to believe that Hinton's novels, including Rumble Fish, are realistic portraits of average American teenagers. He commented that the books' popularity is largely due to their action-packed narratives, simplistic plot structures, intense emotional tone, and well-defined principles. He noted that adults are rarely present and that girls also play only vague cameo roles: "In this world the stories, like the streets, belong almost exclusively to tribes of adolescent males."

In her defense, Hinton commented in an interview in Seventeen:

I started writing before the women's movement was in full swing, and at the time, people wouldn't have believed that girls would do the things that I was writing about. I also felt more comfortable with the male point of view—I had grown up around boys.

Malone commented that he was mystified by others' claims that Rumble Fish and Hinton's other books are realistic and that, in his opinion, because of their lack of reality, "despite their modern, colloquial tone, [Hinton's books] are fairy tale adventures" and the gang fights in them are "as exotic as jousts in Ivanhoe or pirate wars in Treasure Island."

To bolster his case that the novels are mythic, he noted that the settings are vague; the action could take place anywhere. In addition, the novels' setting in time is also hard to pin down.

Malone also described Hinton's prose style as being at times "fervid, mawkish and ornate" and said that the morals in her fictional universe are "as black-and-white as an old cowboy film."

In the Times Literary Supplement, Jane Powell commented that the book is disappointing because of Rusty-James's victimization and his evidently doomed fate. As she notes, by the end of the book, "There can't even be a glimmer of hope for the future."

Hinton revealed in the production notes to the film version of the book that the book was difficult to write because of the contrast between Rusty-James, who is a simple character, and the Motorcycle Boy, who "is the most complex character I've ever created.... It's about over-identifying with something which you can never understand, which is what Rusty-James is doing. The Motorcycle Boy can't identify with anything."