This is a series of science fiction stories and novels that take place over a fairly long period of time and in different parts of the universe. In general, the main characters and settings differ in each of the works.
Bold type indicates a book I've read.
"The Sentinel" (written in 1948, first published in 1951 as "Sentinel of Eternity")
"Encounter at Dawn" (first published in 1953)
2001: A Space Odyssey (1968)
2010: Odyssey Two (1982)
2061: Odyssey Three (1987)
3001: The Final Odyssey (1997)