Complex sentence: From 1942 to 1946, a series of morally ambivalent costume melodramas were produced by Gainsborough for the domestic market mostly based on recent popular books by female novelists.
Split into simpler sentences: From 1942 to 1946, a series of morally ambivalent costume melodramas was produced by Gainsborough for the domestic market. They were mostly based on recent popular books by female novelists.