Some more today: Heraldry For The Designer by William Metzig, published in 1970. (thanks to the recommendation of a fellow heraldist) It’s an interesting book. His style is unique but some of his ideas about heraldry border on the bizarre.
Also Royal Ceremonies of State by J.P. Brooke-Little (quondam Clarenceux King of Arms) published in 1980. As the title states its a book mostly about British royal ceremonies. However, the author being who he is there is a chapter on the Heralds and a good bit of heraldry throughout especially in the chapters on funerals and orders of chivalry. It’s also a book that illustrates well that the function of a herald isn’t limited to genealogy and the devisal of coats of arms. There are an extensive amount of ceremonial duties involved with being a herald.