The scope of The Greenwood Encyclopedia of Science Fiction and Fantasy was defined early on as 600 entries written by a number of different authors, ranging from established specialists to doctoral students.

With the acknowledgement that the editors subjective tastes significantly influenced the selection of topics, he concluded that the work is one of the "stars in the expanding university of science fiction studies".

[4] Aaron Parrett, reviewing this work for the Science Fiction Studies in 2006, suggested that it is too limited in scope, and "reflects the idiosyncratic state" of its editor, criticizing the choice of the term encyclopedia in the book's name as misleading.

He blamed Greenwood's editorial board for "thwarting a solid survey of a literary field" by limiting this project to 600 entries, particularly given that the book already combines two genres (science fiction and fantasy).

He did note that "there is plenty here to enjoy and appreciate", highlighting a number of "delightful" entries, and concluded by resigning himself to the fact that by default, any encyclopedic project "that aims for anything less [than everything] will be inevitably limited in scope".

He nonetheless acknowledged that "the general quality of the entries is good", and in particular praised "the geographically-themed articles" about different parts of the world, such as "Asia" or "South Pacific", as well as those on niche topics, such as the "Rats and Mice", although he also cautioned that their inclusion can make the work "too ephemeral" on occasion.

[1] Steven J. Corvi reviewing the Greenwood Encyclopedia for The Journal of Popular Culture in 2007 likewise noted the book is overpriced (at $349.95) and therefore is not likely to be easily accessible to most casual readers.

Nonetheless, he concluded that "these faults do not offset the usefulness of this work", and that it is "an essential tool for students writing thematic essays", and teachers planning relevant lessons.