(from my amazon UK review august 2007)
The author's Bloody April (2005) was a fine historical account of the air war in the Arras sector in 1917. It showed how the romantic view of the war in the air as being fighter versus fighter was no longer true--two-thirds of the British planes in that sector were two-seaters, and the primary role was photo reconnaissance and artillery spotting, with trench-strafing, anti-balloon attacks, and bombing playing a secondary role. The fighters were used to protect the two-seaters and to prevent German photo recon and artillery spotting. The British were willing to accept very heavy losses to accomplish strategic goals.
Aces Falling shows how the air war doctrine of 1917 evolved further. Photo recon and artillery spotting are still vital, but in 1918 there was a need to help lessen the impact of the German ground offensives. Trench strafing and anti-balloon attacks played a greater role at the front, and now strategic bombing was employed against bridges, rail depots, etc, to help hinder to movement of men and supplies to the front. Airfields were also a prime bombing target. Bombing raids with 50 or more aircraft were not uncommon--but would have been unthinkable even in 1917. By 1918 the strategic doctrine was not unlike that in WW II. But bombs were small (about 112 lbs max) and bombsights nonexistent.
The role of the romantic fighter ace was disappearing. The "lone wolf" approach ceased to be effective when the wolf ran into a group of a dozen enemy fighters. If the fighter pilot remained with his squadron, a dogfight might involve two dozen or more aircraft: accidents and stray bullets were dangers that not even the most skilled of the aces could always avoid. Ground fire was becoming increasingly effective and deadly--descending to low altitude to check a downed enemy was asking for serious trouble. Many of the great aces died: strategy was replacing tactics.
Bloody April had a lot of technical detail about the aircraft and the training--this helped illustrate the mismatch in equipment between the Germans and the British, and it provided a fascinating look at how, nonetheless, the British were able to win the battle. Aces Falling has less technical detail, which is a bit disappointing, but there was much less of a mismatch in the equipment in 1918. So--read the book, and if you haven't read Bloody April, grab that as well.