The Unbearable Lightness of Being is a surprisingly successful film adaptation of Czech author Milan Kundera's demanding 1984 bestseller. Daniel Day-Lewis stars as an overly amorous Prague surgeon, while Juliette Binoche plays the waiflike beauty whom Lewis marries. Even though he's supposedly committed, Lewis continues his wanton womanizing, notably with silken mistress Lena Olin. Escaping the 1968 Russian invasion of Prague by heading for Geneva, Lena takes up with another man, and unexpectedly develops a friendship with wronged wife Binoche. Meanwhile, Day-Lewis, who previously was interested only in sex, becomes politicized by the collapse of Czechoslovakia's Dubcek regime. Unbearable Lightness of Being may be too leisurely paced for those accustomed to the roller-coaster rhythm of a Steven Spielberg film, but other viewers will leave the theater with the same warm sense of inner satisfaction that is felt after finishing a good, long novel.