Accompanying its text were numerous black and white photographs illustrating authors, book and magazine covers, film and TV stills, and examples of artists' work.

The encyclopedia is updated regularly (usually several times a week) by the editorial team with material written by themselves and contributed by science fiction academics and experts.

Though the SFE is a composite work with a considerable number of contributors, the three main editors (Clute, Langford and Nicholls) have themselves written almost two-thirds of the 5.2 million words to date (September 2016), giving a sense of unity to the whole.

It is the Britannica of the sf field", positively commenting on the breadth and scope of the entries, and even the illustrations, which are informative, and not just decorations.

[9] Edward James, a British scholar of medieval history and science fiction, praised the second edition of the encyclopedia in his review (also for the journal Foundation) in 1993, writing that it is "the one indispensable volume on every sf readers' shelf: not only the best reference work in the field, but one of the best reference works I have seen in ''any'' field".

James also noted that although the project is a collaborative effort, nearly half of the entries for that edition have been written by Clute, which he saw as a very impressive achievement on his part.

Nonetheless he noted that the volume is not perfect, and contains some errors as well as several entries on novel topics that could use more grounding in prior research before being written about in an encyclopedia".

[11] Briefly commenting on the third edition, Andrew M. Butler called it "a gold standard for reference works in the field".