THE ENTIRE PLOT, said Holmes, concerns the curious incident of the able successor to Arthur Conan Doyle. But, said an incredulous Watson, there is no able successor to Conan Doyle. Exactly, replied Holmes.

Ronald C. Weyman's Sherlock Holmes & the Ultimate Disguise (Simon & Pierre, 139 pages, $15.95 paper), however, is as good as if not better than the wave of flaccid duplications of the Sherlock Holmes stories that followed in quick and almost ghoulish succession after the death of Conan Doyle. The monomaniacal Sherlockians, of course, would have us believe that Doyle was merely Dr. Watson's literary agent. Weyman takes a different and more interesting approach, following Holmes to Canada after his mock death at the Reichenbach Falls. He has a delicious ability to recreate late Victorian Ontario - the Toronto and Kingston of the tentative yet ebullient 1890s - and fills the cities with a cornucopia of travelling circuses, secret papers, and murderous denizens of the Canadian demi-monde.

Weyman's depiction of Holmes and Watson is similarly convincing. While lacking the intangible charisma and style that permeated Conan Doyle's writings, Ronald Weyman does manage to convey the core and crux of his hero, the quintessential wit and almost manic genius. The story itself is satisfactory if not scintillating - it is important to remember, however, that at least a quarter of the authentic canon contains rather feeble story-Iines.

Conan Doyle? Absolutely not. An intelligent and competent imitation? Very much so. Well worth the read.