This short masterpiece tells of love, betrayal, and a search for real meaning in life. Kitty is an attractive middle class Brit. The only real future for her is to marry well. But when she finds none of her suitors quite up to her hopes, and with her younger sister becoming engaged, she succumbs to the pressure and agrees to marry Walter, a man who adores her, but whom she finds boring. He takes her with him to Hong Kong where he works as a bacteriologist.
There is much here about class. One hero of the story is mother Superior, the head of a corps of nuns dedicated to caring for the sick and the poor. She had been brought up in a very wealthy family in France, but found a purpose in life beyond her personal needs. So too Walter, a shy biologist who risks life and limb to try to stem a cholera epidemic in the interior of China.
Maugham offers musings on religion without sounding excessively preachy, and offers a considered view on what makes life worth living. It is a joy to read and to watch as Kitty comes of age, learning from the people she encounters and ultimately sees past the veil of her life to some underlying truth.. There are also comments here on the nature of westerners "doing good" in cultures considered lesser.
Walter's dying words are "It was the dog that died." This is a reference to the poem "An Elegy on the Death of a Mad Dog" by Oliver Goldsmith. There are various interpretations to be had of the significance of this. The poem tells of a man who is bitten by a mad dog. Yet it is not the man who dies but the dog. In the novel, I believe that Walter sees himself as the mad dog who had dragged Kitty into a life-threatening situation, (foreshadowed by Maugham's prologue) biting her in a way, expecting that it would be a death sentence for her. Instead it was Walter who would pass, thus the irony. (Here is a link to the poem - http://www.online-literature.com/oliver-goldsmith/2090/)
The title offers a nice field in which one can play the game interpretation. The title comes from a poem by Shelley, "Lift Not the Painted Veil Which Those Who Live" (http://poetry.poetryx.com/poems/543/). The notions offered in the novel have a primary source here.