Nick, regarding language: I would take the English as found on original test reports e.g. on
www.aircraftperformance.org any day over current British Oxford English. Or any printed publication of that era. Back then it was e.g. "Mr. Sydney Camm, O.B.E.,...", today an intolerable (worthy of capital punishment) "Mr Sydney Camm OBE..." (correct example taken from a caption in Flight magazine).
I agree with Stig that significant amount of additional text would be possible to be included if the layout eliminated the blank spaces that serve no useful purpose. E.g. the old Profile-series or the classic Aerofax-series are brilliant examples on how to maximize space while maintaining excellent readability.
However, Ospreys´s older aviation-related series - that is Aircraft of the Aces, Combat Aircraft and Aviation Elite Units - are not awful in this respect. However, the new Air Vanguard and the naval titles of the New Vanguard are thus far quite hopeless. The Air Vanguard would be quite OK, if the series followed the idea of e.g. Monogram Close Up -series, i.e. concetrated on design and development, not trying to cover everything.