You raise an interesting question, and giving this some thought I arrived at the following conclusion; A really good and interesting book would be one that was beautifully illustrated and showed some of the classic 'house styles' and variations that are typical to some makers. Some examples would be;
Holland and Purdey's 'house' engraving styles
Woodwards's arcaded fences
Rigby's dipped edge locks
Lancaster and Hollands 'leg of mutton' locks
Westley Richards 'drop locks' and style of opening lever
Powell's push up opening lever
Greener's side safety
Boss's single trigger and selector
Churchill's house engraving and pinless locks
Back on topic, Donald Dallas and Douglas Tate have both done fine specialist books, and the Vic Venters book mentioned is also very good. Diggory Hadokes books are good, but the illustrations are more B&W, though good nonetheless.
