A novel by RobertHeinlein
Heinlein's last book. The culmination of the saga of LazarusLong and his extended family.
In the end, characters from most of the books Heinlein wrote during his life are gathered together on the planet Tertius, including characters from incompatible "realities".
Title taken from (or referring to, however you want to look at it) Alfred, Lord Tennyson's poem Ulysses.
Relevant excerpt (lines 58-61):
Push off, and sitting well in order smite The sounding furrows; for my purpose holds To sail beyond the sunset, and the baths Of all the western stars, until I die.