SET IN southwest China and Tibet at the turn of the last century, Tulku is an exciting, beautifully written adventure story which intelligently illuminates, in the course of its narrative, a number of different spiritual perspectives and mystical ideologies.

Its hero is Theodore Tewker, the 14-year-old son of American missionaries, whose mother died when he was four. Born in China, Theodore has grown up in a settlement founded and run by his father, the minister of an austere Christian sect called the Congregation of Christ Jesus. The book opens during the Boxer rebellion when armed bands of Chinese dissidents were regularly pillaging the countryside, in the very first chapter, Theodore's settlement - which is not merely the only home, but also the only spiritual reality he has ever known - is attacked and completely destroyed. Theodore is the sole survivor.

Enter Mrs. Jones, a horseback-riding, rifle-shooting, free-thinking, plain-speaking middle-aged English botanist, accompanied by her guide - a poetic Chinese boy in his 20s, named Lung.

Obviously, the characters, whose lives and destines are joined together at this point, could not be more disparate. Nor could their adventures be more compelling. Led by the valiant, even comic, Mrs. Jones, the trio traverses the mountains and, pursued by bandits, crosses into Tibet.

There, in the rarefied air of the Tibetan Hinalayas, they are rescued by a high Tibetan lama escorted by a group of armed monks. The Lama, as it turns out, is also on a quest; a quest even nore bizarre than Mrs. Jones search for exotic botanicals, He seeks a child who, signs will indicate, is the [WORD ILLEGIBLE] of the Siddha Asara, "in his latest body" abbot of the great monastery of Dong Pe. The Lama explains the Buddhist theory thus:

"There are certain great souls who, though they have reached enlightenment, choose to continue in the world of death and birth in order that they may show their fellow creatures the path to freedom which they themselves have chosen. And these men have reached such spiritual mastery that they can overcome the forgetfulness which ordinary souls experience at death and birth."

At first, because of certain unmistakable signs attending the travelers, the Lama supposes that Theodore is the child he seeks, but, after several days of observing him, changes his mind. He then correctly deduces that Mrs. Jones is pregnant with the Tulkuto be - a fact not even she is aware of. But, since Mrs. Jones' love affair with Lung was not the least of the hardships Theodore had to contend with during their long journey, no one can deny that the possibility exists, and, by the time they reach the monastery, it is a confirmed fact.

"'I have been to Llasa and seen the great Potala,' intoned the Lama in his clanging Mandarin. 'I have travelled in India and seen the mighty shrines of that land. I have seen even the sea. But in all this world of illusion I have seen no illusion that can compare with Dong Pe."

The best part of this excellent novel takes place in the monastery. Here, Dickinson's extensive knowledge and appreciation of Tibetan temple are and architecture add dimensions to the story, while his clear grasp of the principles of Tibetan Buddhism give it unusual depth. The author is never didactic; though he explains things with great care, the momentum of the story never flags. What is more, his characters never lose their integrity because each one is affected by what happens in the monastery according to his or her level of spiritual development. It is this, even more than the brilliant descriptions and careful explanations, which gives this amazing story its ring of truth.