Complex sentence: The best-known example in the recent past is the Kennedy assassination conspiracy literature, though similar material exists concerning the September 11 attacks, the crash of TWA Flight 800, and the spread of AIDS in the black community.
Split into simpler sentences: The best-known example in the recent past are theories about a conspiracy causing the Kennedy assassination, as reflected in its literature. Similar materials have been developed discussing conspiracies as the cause for the September 11 attacks, the crash of TWA Flight 800, and the spread of AIDS in the black community.