Over his half-century career, Grand Master of Science Fiction Robert A. Heinlein (1907-1988) produced some 40 book-length works and collections of shorter material, much of which has remained in print over the decades.
For younger readers
Rocket Ship Galileo - 1947 (juvenile)
Space Cadet - 1948 (juvenile)
Red Planet - 1949 (juvenile)
Farmer in the Sky - 1950 (juvenile)
Between Planets - 1951 (juvenile)
The Rolling Stones - 1952 (juvenile)
Starman Jones - 1953 (juvenile)
The Star Beast - 1954 (juvenile)
Tunnel in the Sky - 1955 (juvenile)
Time for the Stars - 1956 (juvenile)
Citizen of the Galaxy - 1957 (juvenile)
Have Space Suit - Will Travel - 1958 (juvenile)
Podkayne of Mars - 1963 (juvenile)
The Future History series
The Man Who Sold the Moon - 1950
The Green Hills of Earth - 1951
Revolt in 2100 - 1953
Methuselah's Children - 1958
Orphans of the Sky - 1963
The Past Through Tomorrow - 1967 (omnibus edition)
The Adventures of Lazarus Long
Time Enough for Love - 1973
The Notebooks of Lazarus Long - 1978 (aphorisms)
The Number of the Beast - 1980
The Cat Who Walks Through Walls - 1985
To Sail Beyond the Sunset - 1985
Other novels
Beyond this Horizon - 1948
Sixth Column - 1949
Double Star - 1956 (Hugo winner)
The Door into Summer - 1957
The Menace from Earth - 1959
Starship Troopers - 1959 (Hugo winner)
Stranger in a Strange Land - 1961 (Hugo winner)
Glory Road - 1963
Farnham's Freehold - 1964
The Moon is a Harsh Mistress - 1966 (Hugo winner)
I Will Fear No Evil - 1970
Friday - 1982
Job: A Comedy of Justice - 1984
Unrelated short fiction and marginalia
Waldo and Magic, Inc. - 1951 (short stories)
Assignment in Eternity - 1953 (short stories)
Expanded Universe - 1980 (essays and short stories)
Grumbles from the Grave - 1989 (posthumous, letters)
Tramp Royale - 1992 (posthumous, previously unpublished travel memoir)
Requiem - 1992 (posthumous, marginalia and tributes from other writers)