The cover of that book features a fellow peering out beyond the stars to see ulterior gears. Boorstin prefaces the book with a quote from Shakespeare:
And take upon one 's the mystery of things
As if we were God's spies.
That charming cover picture is a 19th century illustration, which I only mention since many assume it has some relevance to the Renaissance.
The other books, equally hefty, include The Creators: a history of heroes of the imagination, (1993) which has a painting by Michaelangelo on the cover.
The Seekers: The Story of Man's Continuing Quest to Understand His World (1998) has a picture of god on the cover-- Blake's geometrician god.
Boorstin was a prolific scholar and this last trilogy is a plausible culmination of an interest which manifested itself 30 years earlier, with the study of American history, and The Lost World of Thomas Jefferson (1953).