Leonard Koppett, the Times' presiding sports statistician-theoretician-intellectual (viz. The Thinking Man's Guide to Baseball, 1967), skillfully leads you hand-by-head through the essential rules and trends of big-time team sports (baseball, football, basketball, hockey), individual games (boxing, tennis, golf, horse racing), and those of little commercial clout (lacrosse, swimming and diving, fencing, bowling, etc.). You'll learn how to compute batting averages, how to tell a Straight T from a Double Wing formation, the meaning of' betting combinations such as quinella and exacta, and stats you never knew -- a tennis ball, for instance, should bounce 53"" if dropped on concrete from 100"". There's sensible advice, too; the current crop of football widows will cotton to Koppett's imperative that understanding football begins with ignoring the jargon and duffers will agree that golf is fundamentally a game of self-control. Auto racing is not included in the book (a prejudice?) and when Koppett talks about hockey players skating bareheaded he doesn't mention the ongoing helmet controversy, but these are quibbles with an otherwise deserving handbook. This is for beginners, youngsters, wives -- and aficionados who like their sport cerebral will find Koppett instructive, too.