i don't know why they called it 'so-and-so units'. they don't really talk about the units. it is more the operational story of the airplain, with a short introduction about origins and development.
about this specific book, i'm not a particular fan of barret tilman's. i found all his book so far kind of boring. it could be me, i admit. i just hoped that for sbd he would make an exception. i don't think he did.
readable, with some yawning.