The novel, conceived by Nabokov before moving to the United States (the passages “Ultima Thule” and “Solus Rex” were written in Russian in 1939), is structured as a 999-line poem with commentary replete with literary allusions. This structure was suggested to Nabokov by his work on a four-volume commentary on the translation of “Eugene Onegin” (a possible prototype is Alexander Pope’s “The Dunciad”). According to the book, the poem being commented on belongs to a famous American poet, and the commentary was voluntarily added by his university colleague. The colleague, clearly crazy, sees in the poem hints of his own fate - the fugitive king of Zembla. A revolution took place in this non-existent country, and the king fled to America.

(That is, the interactive commentary on the poem is actually the main part of the novel and must be read, as well as the “Preface” written by Nabokov himself and "Index" compiled by him. Notes (links in square brackets) added by the translator.)