"Dr. Strangelove was a nightmare satire; 2001 is, in Kubrick's words, a 'mythological documentary.' One film destroyed the world to alert man that life as he knew it could come to an end; the other created new worlds in its questing hypothesis that man was not the only intelligent form of life in the universe. In its context Dr. Strangelove was weighted with pessimism; 2001 is buoyed up with hope."
-- Alexander Walker, Stanley Kubrick Directs, Expanded Edition (1972 & 1999)

"This is the work of an artist so sublimely confident that he doesn't include a single shot simply to keep our attention. He reduces each scene to its essence, and leaves it on screen long enough for us to contemplate it, to inhabit it in our imaginations. Alone among science-fiction movies, 2001 is not concerned with thrilling us, but with inspiring our awe."
-- Roger Ebert, Chicago Sun-Times

'On the deepest psychological level,' he [Kubrick] said, 'the film's plot symbolized the search for God, and it finally postulates what is little less than a scientific definition of God.' And there you have Stanley Kubrick. Whatever else movies do, they do not postulate definitions; if they try they die. What possible religious revelation could be vouchsafed by a movie whose only memorable character was a gay computer? At this distance, within two years of the title's prediction, 2001 looks dated and bloated; watching the flight attendants on the moon shuttle, I only wish that Kubrick had had the courage to call it 1968: A Bad Year for Hats."
-- Anthony Lane, The New Yorker (March 22, 1999)

"The ridiculous labor of 2001, the cavernous sets, and the special lenses, ride upon a half-baked notion of the origins and purpose of life that a first-year student ought to have been ashamed of. But this message in a bottle lasts over three hours, and the movie has long sequences of directorial self-indulgence."
-- David Thomson, A Biographical Dictionary of Film (1994)

"... [T]he most awesome, beautiful (the visuals and the music), mentally stimulating, and controversial science fiction film ever made..."
-- Danny Peary, Cult Movies (1981)

"... a kind of space-Spartacus and, more pretentious still, a shaggy God story."
-- John Simon, New Leader (May 6, 1968)

"It's a monumentally unimaginative movie... The light-show trip is of no great distinction; compared to the work of experimental filmmakers like Jordan Belson, it's third-rate. If big film directors are to get credit for doing badly what others have been doing brilliantly for years with no money, just because they've put it on the big screen, then businessmen are greater than poets and theft is art."
-- Pauline Kael, Harper's (February, 1969) anthologized in her collection For Keeps (1994)

"The least that can be said for Stanley Kubrick's 2001: A Space Odyssey is that this production is an overwhelming visual experience, supplemented by an imaginative use of all the divergent elements which go into filmmaking. The most that can be said for this MGM roadshow presentation in Cinerama, filmed in Super Panavision and Metrocolor, is that once again, as so rarely happens in film history, an individual talent -- Kubrick -- has widened and exalted the art of the film by his vision, dedication and uncompromising creative approach to the medium so often called the 'synthesis of all art forms.'"
-- Jim Watters, Boxoffice Magazine (April 8, 1968)

These books are available from Amazon.com:

A Biographical Dictionary of Film (1994), by David Thomson
Cult Movies (1981), by Danny Peary
Stanley Kubrick Directs, Expanded Edition (1999), by Alexander Walker
Roger Ebert's Video Companion 1998, by Roger Ebert
For Keeps (1996), by Pauline Kael