The Nature of Gothic, the chapter in The Stones of Venice/John Ruskin described by Kenneth Clark (father of Alan) as one of the noblest things written in the 19th century: "Even now, when the ideas it expressed are accepted and the cause it advocates is dead, we cannot read it without a thrill, without a sudden resolution to reform the world."
A dense read: an analysis of Gothic architecture and pattern with detailed instructions on how to interpret a Gothic building Below: a painting of the west front of St Mark's by J W Bunney. Ruskin commissioned the painting as a strict architectural record. The artist apparently spent 600 days working on it.
"Lastly, Read the sculpture. Preparatory to reading it, you will have to discover whether it is legible (and, if legible it is neatly certain to be worth reading). On a good building, the sculpture is always so set, and on such a scale, that at the ordinary distance from which the edifice is seen, the sculpture shall be thoroughly intelligible and interesting...
... the criticism of the building is to be conducted precisely on the same principles as that of a book and it must depend on the knowledge, feeling , and not a little on the industry and perseverance of the reader, whether, even in the case of the best works, he either perceive them to be great, or feel them to be entertaining."