The book has been praised by other science fiction writers. Karl Edward Wagner cited The Day of the Triffids as one of the thirteen best science-fiction horror novels.[11] Arthur C. Clarke called it an "immortal story".[12] Anthony Boucher and J. Francis McComas praised it, saying: "rarely have the details of [the] collapse been treated with such detailed plausibility and human immediacy, and never has the collapse been attributed to such an unusual and terrifying source".[13] Forrest J. Ackerman wrote in Astounding Science Fiction that Triffids "is extraordinarily well carried out, with the exception of a somewhat anticlimactic if perhaps inevitable conclusion".[14]
Brian Aldiss coined the disparaging phrase cosy catastrophe to describe the subgenre of post-war apocalyptic fiction in which society is destroyed save for a handful of survivors, who are able to enjoy a relatively comfortable existence.[15] He singled out The Day of the Triffids as an example and described Triffids as "totally devoid of ideas".[16] However, some more recent critics have argued against this view. Margaret Atwood wrote: "one might as well call World War II—of which Wyndham was a veteran—a 'cozy' war because not everyone died in it".[17]
John Clute commented that the book was regularly chosen for school syllabuses, as it was "safe".[16] Robert M. Philmus called it derivative of better books by H. G. Wells.[16] Groff Conklin, reviewing the novel's first publication, characterised it as "a good run-of-the-mill affair" and "pleasant reading... provided you aren't out hunting science fiction masterpieces".[18]
