In 1899, he published his two-volume book, Histoire de l'architecture. In it, he developed isometric drawings that combined plan, elevation, section, perspective into a single drawing. He then used this visual approach to describe buildings in social and material terms along with historical determinism.[1]
In 1904, he won the RIBA's Royal Gold Medal. Very important for the study of Greek architecture was his contribution "Le pictoresque et l'art grec" (chapter in The history of architecture).
Choisy died on September 18, 1909, at age 68, in Paris.