The book is a reprint of a cult text of post-1968 psychedelic culture: The Rainbow Book, published in 1975 in Berkeley, California, on the occasion of The Rainbow Show exhibition held at the Fine Arts Museums of San Francisco.

The Rainbow Book is a collection of essays and illustrations devoted to the rainbow and color spectra, analyzing the significance of color (both physical and metaphysical) from antiquity to modern times.

An encyclopedia of the cultural and artistic manifestations of the rainbow: in myth, magic and paintings, as well as in prints and poems. The book includes poems by Virgil, Dante, Blake, Keats, Wordsworth, and others; paintings by Giotto, Bosch, Van der Weyden, Dürer, Rubens, Blake, Turner, Constable, and Church; and the sacred art of Tibet.

The book is printed on sheets of different colors, according to the rainbow spectrum, and reports notions of increasing complexity, accessible at first to younger readers and later to the more experienced and interested in the subject.

The reprint accompanies the exhibition Rainbow. Colors and Wonders between Myths, Arts and Science at MUDEC in Milan (February 16–July 2, 2023), and the release of the first issue of MUdec United.