In the literature of commercial aviation, one name dominates: R.E.G. (Ron) Davies, a curator at the National Air and Space Museum who has made a long and prodigious career documenting in detail the histories of Continental, Pan Am, Delta, Lufthansa, Aeroflot, TransBrasil... You get the idea. These days, Davies publishes books on individual airlines via his own company, Paladwr Press.
Of his overall histories, his grandest include Airlines of Latin America since 1919 (Smithsonian Institution Press, 1984), Airlines of the United States Since 1914 (Putnam, 1972), and History of the World's Airlines (Oxford, 1964). As for a few non-Davies classics:
Bonfires to Beacons by Nick A. Komons (Smithsonian, 1978). A scholarly look at the U.S. government's role in developing commercial aviation.
Sky Gods by Robert Gandt (Morrow, 1995). A Pan Am pilot recounts the dramatic story of his airline's fall.
Airways: The History of Commercial Aviation in the United States by Henry Ladd Smith (Knopf, 1944). The title says it all (but note publication date).
Fate Is the Hunter by Ernest Gann (Simon and Schuster, 1961). A pilot's-eye-view of the thrills and dangers of commercial aviation in the 1930s.
Conveying the concept of "space" to an audience with essentially no first-hand experience of it is a mission that requires both vivid writing and patient explanation.
Test Flight and Exploration
At the Edge of Space : The X-15 Flight Program by Milton O. Thompson (Smithsonian Institution Press, 1992). An insider's account, garnished with Thompson's impish sense of humor, of one of the most successful research aircraft ever flown. Thompson, along with Scott Crossfield, Neil Armstrong, and other legendary test pilots, flew the hypersonic rocket-powered X-15 in the 1960s, and these flights provided essential lessons for planners and pilots of the first manned excursions into space.