British crime novelist Thomson, author of four collections of Holmes short stories, combines the canonical facts with the best of recent scholarship in this winning dual biography of that Victorian odd couple, Sherlock Holmes and his chronicler, Dr. John H. Watson. Unlike many Holmes biographers, the author trips lightly over data where it is vague, inconsistent or nonexistent, consigning discussion of such pedantic matters as problems of dating and the location of 221B Baker St. to appendices. In her prologue she just as deftly puts to rest the claim that the relationship between the two men was homosexual. Not content simply to cite higher authorities, Thomson with unobtrusive modesty puts forward her own theories on such hotly debated issues as the identity of the king of Bohemia and the second Mrs. Watson. Applying modern psychology, she makes the elementary deduction that the great detective was manic-depressive, but is also diligent in documenting other sides of his complex character such as the sentimental keeping of Irene Adler's picture. One advantage of the book's chronological approach is that the reader sees Holmes's character mature, from the impetuous young man of A Study in Scarlet to the mellow 60-year-old who takes his last bow at the start of the Great War. This is one of the finer case studies of one of literature's most celebrated friendships. (Mar. 1) Forecast: A future classic of Holmesian higher criticism, this book will attract ordinary fans looking for a readable narrative, not just Baker Street Irregular diehards.