As a boy, I loved those little books because they had colourful covers and catchy titles which effectively dissipated my depression from overwhelming communist greyness. Besids, I was really interested in war and military topics.
Examples of titles:
Chasing V-1 The Ghosts of the Jungle Human torpedoes The Annihilation of Pearl Harbour Kamikaze - Airmen of Death The Lonely Fortress
They provided me with knowledge about many WW2 facts, especially concerning Poland. E.g., the Defence of the Post Office in Gdańsk.
or September 1939 campaign
In some books the authors smuggled in communist propaganda, stressing the greatness of the Red Army, but the books which described the war in the West were quite objective.