There's a wealth of literature on bombing campaigns of the Second World War (at least in Europe), though specific focus on air defence is less common. As a starting point I'd suggest Richard Overy's The Bombing War: Europe 1939-1945 for an overview of all aspects including civil and military defence, primarily in Britain and Germany though other European states and the Soviet Union are covered. The first half of Germany and the Second World War: Volume VII, The Strategic Air War in Europe and the War in the West and East Asia 1943-1944/5 is Horst Boog's analysis of the key phase of the Combined Bomber Offensive including "Defending German Skies, Part of the Overall Air-War Problem: From Early 1943 to the Invasion in 1944".

Moving into popular history, if you're after a single volume on German Air Force efforts then Donald Caldwell and Richard Muller's The Luftwaffe Over Germany: Defense of the Reich might be your best bet. There are also numerous works on particular aspects; to pick a few, Theo Boiton researches night fighters extensively and has written Battles with the Nachtjagd: The Night Airwar Over Europe 1939-1945 with Martin Bowman as an overview in addition to an ongoing (11 volumes so far) Nachtjagd Combat Archive series cataloguing all engagements. On the ground, there's Edward Westermann's Flak: German Anti-aircraft Defenses, 1914-1945. The rapidly evolving electronic battleground is covered in Alfred Price's Instruments of Darkness: The History of Electronic Warfare, 1939–1945.

I'm afraid I have very little covering campaigns outside Europe; Steven J. Zaloga's Defense of Japan 1945 in Osprey's Fortress series gives a brief overview, and has a reasonable bibliography for further reading, but there isn't nearly as much literature in English.