Just got the three books in the series--they cover British tanks from World War One through the end of World War Two, and represent a tremendous value for money. The first title covers the First World War and the interwar years, and the second and third cover British-built tanks and American-built tanks in British service.
Unlike earlier compilations, they haven't just glued together a bunch of Osprey Vanguard titles--there is a certain amount of amalgamation, and some material was written to bridge gaps. You don't get every single color drawing in the equivalent Vanguard titles, nut you get quite a lot of them. The principal author is The Tank Museum's David Fletcher, but Steve Zaloga did write some of this title.