Meet Pafnuty Lvovitch Tschebyscheff: patron saint of the author; distinguished Russian mathematician; and bearer of a moniker that becomes the thread of a marvelously tangled tale likely to please those of playful intelligence, mathematicians or not. Davis, professor of applied mathematics at Brown, reveres T. because of his brilliant contributions to many fields of mathematics (a polymath!), but especially to the theory of approximations, which deals with the ability to express complex equations and curves by simpler formulas or linear expressions. (Such approximations are at the very heart of today's computers.) Davis wrote a text on approximation theory that sparked an admiring letter from a fellow-mathematician, but a distinctly dissenting view on the spelling of the Russian name. In defense of his personal transliteration, Davis cites his early imprinting with that form as he pursued Russian literature. He goes on to describe not only the surname, but the man and his familial name, Pafnuty. True-life adventures follow--with coincidences and chance encounters that find Davis in Tasmania, the Middle East, and other exotic spots (good mathematicians travel a lot). Various twists in the thread disclose that Pafnuty derives from an early Christian father, Pafnutious. He, it seems, is none other than the famous anchorite others call Serapion or Athanael, the monk who converted ThaÃ¯s. (Massanet's librettist could find only two rhymes for ""Pafnuce,"" so he's Athanael there too.) On his way back from Tasmania, Davis stops off in Israel where he bumps into a former student who tracks down further leads on Pafnuty, climaxing in the discovery of a hieroglyph-source and the poisoning of a fellow-diner at an obscure restaurant. . . with a pseudonym, Babnuda, that's yet another variant on Pafnuty. Back at Brown, Davis recounts still other adventures and pursuits. A book without a plot cannot be summarized altogether coherently; but it can, in this case, be read delightedly.