What to read after Giotto's O?

Andrew Ladis begins his book with Giorgio Vasari's famous story of Giotto's O, in which the artist drew a perfect circle freehand, baffled Pope Benedict XI's foolish messenger, and demonstrated his artistic brilliance to those qualified to understand. The fundamental premise of Ladis's work is that the Arena Chapel, like Giotto's mythical O (or tondo), must be understood as a complete, unified whole. He tells us, "the cycle of murals in the Arena Chapel has a depth that underpins the whole, an unpretentious profundity manifested in a formal order, and as in the case of the O, one must have the wherewithal to discern Giotto's achievement beyond the directness and emotional power of the narrative." Ladis does not write about the program from the more expected standpoints of patronage or audience, or via extensive analysis of archival source material. Instead, without discounting the former approaches, Ladis considers Giotto's conception of the Arena Chapel in terms of biblical exegesis, a central geometry, and what he sees as the program's carefully planned symmetry. He urges the viewer to abandon the temporal narrative and follow "visual cues that encourage readings that transcend narrative time," and so he moves through a discussion of Giotto's frescoes, offering new insights about particular passages and continually considering how the meaning of each section resonates with others throughout the chapel.