A story reaching the heart of India; Clear Light of Day, By Anita Desai. New York: Harper & Row. $11.95.

Although "Clear Light of Day" is less than 200 pages long, and although there is almost no plot, it has the presence and power of a larger, weightier novel. Indian Anita Desai writes of her country, and, although not well known in America ("Fire on the Mountain," a previous novel, was published in the United States), her work has received numerous awards in England, including a Booker Prize.

This is a novel of perfect detail, of looking at the world through a magnifying glass, of collecting enough small bits to make sense somehow of the whole. For post-partition India is so complex, so troubled, so awesome that the details (from rotting fruit in the garden to the heat so intense it quells not only movement but ambition) are the best road to understanding.

The story begins when Tara, in her 40s, returns from Washington with her diplomat husband to visit her family in Old Delhi.In the Das family house live older sister/history teacher Bim, and Baba, a brother who never grew up. There is also a neglected garden, a well where a cow drowned long ago, and lots of memories -- memories we sometimes learn about through floating isolated sequences, and sometimes through the characters' struggles to find reality in the rose-colored recollections. Tara, for example, "could not believe the long-remembered, always-remembered childhood had had a backdrop as drab as this, 'we used to likem playing here -- in the dust and mud. What could we have seen in that muddy little trickle? Why, it's hardly a river -- it's nothing, just nothing.'"

"Clear Light of Day" is also about separation. There is the separation of India as an imposing backdrop, and so many separations within the Das family that division is considered from norm.

The parents, what with bridge and business (in that order) were away more often than not. And the children begin splitting up early when brother Raja opts, out of admiration for the rich Muslim neighbors, to take his education in Urdu instead of Hindi. When he follows those neighbors to a distant city, marries their dagughter, and becomes the landlord of the Das family home, the separation, from Bim anyway, appears permanent.

While, spinster Bim is tied to the old house, to Baba, and to all troubled members of the family in ways even she doesn't seem to understand, timid Tara knows she will take the first opportunity to leave. When she married Bakul he not only took her away, he transformed her "into an active organized woman who . . . [checked] her engagement book every morning."

But above all else, to the Das family there is Old India and then there is the rest of the world. Bim challenges Bakul about his portrayal of India to the outside world.

"I refuse to talk about famine or drought or caste wars -- or political disputes. . . .I can discuss such things here, with you, but not with foreigners , not in a foreign land. There I am an ambassador and I choose to show them and inform them only of the best, the finest."

"The Taj Mahal?" asked Bim.

"Exactly," said Bakul."The Taj Mahal, the Bhagavad-Gita, Indian philosophy, music, art, the great, immortal values of ancient India. Why talk of local politics, party disputes, elections malpractices . . . When such things will soon pass into oblivion? Thesem aren't important, when compared with India, eternal India --"

"Yes, it does help to live abroad if you feel that way," mused Bim . . . . "If you lived here . . . I'm not sure if you could ignore bribery and corruption , red-tapism, famine, caste warfare and all that. In fact, living here, working here, you might easily forget the Taj Mahal and the message of the Gita."

"Clear Ligh of Day" contains no famine or corruption, nor does it contain the Taj Mahal, the Bhagavad-Gita, or other symbols of India. Yet its spirit reaches to the very heart of India and of humanity.