The First Book of Urizen (later titled just The Book of Urizen) contains twenty-eight etchings colored with watercolor and printed in orange-brown ink. The mythical character of Urizen, one of Blake's most important creations, appears in no fewer than eight of Blake's books, beginning with Visions of the Daughters of Albion (1793). Variously identified as "Prince of Light, " "Creator of Man," and "primeval Priest," Urizen, clearly representative of God, though not synonymous, was a son of Vala, goddess of nature. Usually depicted in solitude in a cave or on a rock, the morose and wrathful Urizen writes out his laws in books of brass, iron, silver, or gold. Not a positive figure of authority, the name brings to mind "reason," which Blake saw in negative contrast to the power of creative inspiration.

Each of the seven known copies of The Book of Urizen shows a different arrangement (and sometimes different number) of the plates, thus offering seven different narrative sequences. (Other Blake titles reveal the same inconsistency.)

The related books Urizen, Los, and Ahania were later reconstituted as The Four Zoas .

The plate shown represents the fall of Los, entwined in the serpent, Error.