[1] The novel fits in the science fiction genre, describing a post-singularity society, where some humans have evolved further while others chose to remain behind.

Like other works by Dukaj, the novel deals with highly advanced technology (like EPR paradox, related to the Einstein-Rosen-Podolsky bridge) and its implications for human society.

Oramus praised Extensa for a number of reasons: it is a solid science fiction novel, discussing a number of scientific concepts; it is well structured - beginning with a story of a child growing up, and exploding into a story dealing with the entire Universe; the action is dramatic enough; and the themes have significant moral and philosophical dimensions as well.

[18] Also in 2010 (the year a second edition was published), Maria Kobielska reviewed it positively for Polish magazine e-splot, focusing on the narrative style and character development.

He noted that the book is somewhat less "baroque" and complex than some of Dukaj's earlier works, and the theme of contact between more or less advanced civilization is reminiscent of Strugatsky's Roadside Picnic.

She praises the book for interesting discussion of various scientific concepts, as well as world building, although she criticized the main character as "irritatingly passive".