During the early part of WW2 there was a genuine threat and fear of idevastating air raids and they came in force with the Blitz from the middle of 1940 into 1941 and then sporadically thereafter such as the lone aircraft and the Baedecker raids..
Booklets such as these were issued to all homes to prepare the civilian population and help them to survive the raids, other leaflets dealt with what to do after the raid was over, how to purify water and where to get assistance.
Genuine WW2 item, photo shows typical example