The paper reviews the narrative poem Az’’ by S. Petrov (1911–1988), known in his lifetime as a translator of poetry. Published over forty years after its creation, Az’’ is the longest and arguably most important work in Petrov’s poetic legacy. Its vocabulary features nearly all lexical and stylistic registers of the Russian language in existence at the time of the poem’s writing, as well as numerous poetic neologisms. In terms of genre attribution, Az’’ can be defined as a philosophical mystery play. Its protagonist, referred to as Az” [the name of the first letter in Early Cyrillic alphabet that also means the personal pronoun ‘I’], perceives and con- templates the world and interacts with other characters, including seven various alter egos and the Muse. The events constituting the plot of the poem are complex and nuanced, with all the characters trying to elicit and explore Az’’s true identity (i. e., the essence of the human self). However, instead of portraying an autobiographical ego, the poem focuses on a generalized self: its deep examination of ‘I’ deliberately avoids selfishness or egocentricity. The human self is not homogenous: its various facets can conflict with each other, and books may constitute some of its crucial components.