From medieval manuscripts to computer hard-drive folders, trees have for 800 years been important metaphors for organizing knowledge. In “The Book of Trees: Visualizing Branches of Knowledge” (Princeton Architectural), Manuel Lima has selected 200 tree diagrams that make a remarkable variety of subjects understandable. There’s an 1855 organizational chart for the New York and Erie Railroad and an X Men family tree (with a message at the bottom: “Confused? Read More Comics.”). Lima devotes each of the 11 chapters to a different kind of tree map, beginning with figurative trees and ending up at icicle trees.