I have professional interests in the unravelling of the construction history of mediaeval churches and other complex historic buildings and my copy of the 1979 reprint, which I must have bought 35 years ago, is invaluable - as can be said for other editions that I have for Derbyshire and London.
At the moment, I am thumbing through it almost on a daily basis and it still has its original cover and there no signs of it falling apart...