To sail beyond the sunset
by Robert A. Heinlein
SciFi - Subtitled "The Life and Loves of Maureen Johnson (Being the Memoirs of a Somewhat Irregular Lady)". Maureen Johnson is the mother of Woodrow Wilson Smith/Lazarus Long/Theodore Bronson. This memoir takes sexually active Maureen from her childhood in the 1880s to her rescue 100 years later and on to her rejuvenation and activity as a time traveler.
