There is not as much critical commentary on Flowers for Algernon as there is on some other contemporary novels. What criticism does exist has occasionally found fault with the novel on the grounds of sentimentality or predictability, but on the whole the critical response has been favorable. Critics have also noted the novel's status as a work of science fiction.

Typical of the critical response to Keyes's novel is Mark R. Hillegas' 1966 Saturday Review essay, which ranks Flowers for Algel7lon with Kurt Vonnegut's Player Piano and Walter M. Miller, Jr.'s A Canticle for Leibowitz as a "work of quality science fiction," although Hillegas finds the novel "considerably less powerful" than Vonnegut's or Miller's novels. Hillegas also notes that Keyes's novel is occasionally "marred by a clichéd dialogue or a too predictable description." Nonetheless, he finds that the novel "offers compassionate insight into...