 After a seven-year hiatus brought on by poor health, Heinlein produced five new novels in the period from 1980 ("The Number of the Beast") to 1987 ("To Sail Beyond the Sunset").These books have a thread of common characters and time and place.They most explicitly communicated Heinlein's philosophies and beliefs, and many long, didactic passages of dialog and exposition deal with government, sex, and religion.