IN THE SPRING of 1913, an extraordinary shipment was dispatched from Peking to the Bodleian Library at Oxford: 29 crates containing 4 1/2 tons of rare Chinese books, manuscripts and works of art, relics snatched from the disintegration of the Manchu Dynasty. In a single stroke, this acquisition quadrupled the Bodleian's Chinese holdings and made it the leading European library in the field.

The 17,000 items in the collection were the (not wholly altruistic) gifts of an eccentric Englishman living in China, Edmund Backhouse, who was trying to obtain an appointment to the chair of Chinese at Oxford. He seemed eminently qualified for such a position, despite the uncomfortable fact tha he had left the university under a cloud in 1895 without taking his degree.

A master of the Chinese language unequaled in England, coauthor of the widely acclaimed China under the Empress Dowager and of the Annals and Memoirs of the COurt of Peking (then nearing publicaton), Backhouse was equally eminent as a scholar and a practical man of affairs. He had represented various Western business concerns in delicate negotiations with China. Later, in World War I, he was a British secret agent in Peking, trying to purchase weapons badly needed by England. The American Bank Note Company would engage his services in 1917 to secure a contract for the printing of China's paper currency.

As an esteemed (though unpaid) assistant to George Ernest Morrison, the London Times correspondent in Peking who spoke not a word of Chinese, Backhouse had for years been, in a sense, the de facto Times man in China. What England (and to some extent the rest of the world) knew about China in 1913 was known, in significant measure, through the efforts of Edmund Backhouse - much of it confidential information obtained from anonymous, highly placed sources at the imperial court.

In spite of all this, Backhouse never was appointed to the Oxford chair, though he was offered one at King's College, London. Trevor-Roper's biographical study should make Oxford happy from its faculty (though just barely), for this book is as much a detective story as a biography and its gentle but firm conclusion is that its subject was one of the most notable frauds in recorded history.

Oxford might have been suspicious if it had checked the circumstances of Backhouse's abrupt departure in 1895. He left the university and, shortly thereafter, England, in the shadow of a bankruptcy proceeding. As an under-graduate, he had managed to accumulate debts of 23,000 pounds sterling - solid, Victorian pounds sterling - a remarkable tribute to the trusting souls of Oxford merchants.

After Oxford, Backhouse dropped out of sight for three years. He materialized rather mysteriously in Peking in 1898, having acquired several foreign languages (among them Russian, Japanese and modern Greek) somewhere along the way. He still had his Oxford habit of doing things in a big way without much thought of the consequences.

It may have been at Oxford or, even earlier, at St. George's, Ascot, that Backhouse developed the quality that was to lend lustre to his final years: an exquisitely Victorian taste for extravagant, pansexual erotic fantasy. But this quality did not emerge full-brown until near the end of his life, when he was living as a recluse in Peking. A two-volume typescript of his memoirs, written during these final years, was what first put Trevor-Roper on the trail of Backhouse (he was asked to evaluate it as a possible acquisition for the ubiquitous Bodleian). On his first reading, the historian soon discovered that he had in his hand an unusually lavish bit of pornography.

Backhouse claims to have had sexual relations with practically every notable personage in his melieu - his rather varied melieus - from a French master at his school who turned out to be Paul Verlaine, poet and lover of Rimbaud, to the Empress Dowager of China, one of history's truly sinister figures, who bestowed upon him her faded but still lusty favors (she was nearly 70 at their first encounter) between 150 and 200 times. There is more, much more: an Ottoman princess, a sojourn with Tolstoy at Yasnaya Polyana, an affair with a future prime minister, and literary lunches at Oxford with Walter Pater, "discussing 'Greek love' with him, and whether Michelangelo was passive as well as active in that respect."

Alas for Backhouse, it was all a tissue of fabrications - or at least most of it, one can't always be sure, for his fantasy was guided by a scholar's detailed knowledge of his various subjects. But there are clues. In a first draft, for example, he mentioned Rimbaud, but when "an insuperable choronological difficulty" was pointed out, "he defty changed the poet into a cobbler called Rimbot whose name had occasioned a temporary and pardonable confusion."

Examined in the livid light of his memoirs, the earlier life of Backhouse comes into harsh perspective, and it is all of a piece from a Oxford bankruptcy to the final blaze of spurious pornography: brilliant deception every step of the way. He defrauded the British government with false inventories of nonexistent rifles, the American Bank Note Company with a superbly counterfeited contract (in Chinese) to print China's currency.

His masterpiece, and one of the world's masterpieces of forgery evidently, is a central source of China under the Empress Dowager: the diary of Ching-shan, an official of the Manchu court in its declining years, which he claimed to have rescued from looters in the Boxer Rebellion and which was accepted a authentic (though challenged) by a whole generation of scholars. It is in the Bodleian now, at least part of it, beautifully done in a particularly difficult kind of Chinese script (Backhouse was also a master of calligraphy). That august repository seems suitable for this work. It may lack the historic value it once claimed, but surely it has acquired another - as one of the triumphs of the human imagination.