Mr. McGinniss, he of the best-Selling of the President, has written about another nameless writer who, along with a casually annexed young girl, Jennifer, and a friend, Blaine, has been playing the horses for 25 years with a System and a blind assumption that he can win. They go to Hialeah. True about half the whipped excitement here is off the track and in the motel where Jennifer, just as screwy as she is screwable, plays all kinds of games. Actually she wants to be taken very seriously although it is indeed difficult. But then there's the daily outing with the nags and before the sixth day is over, our man is down 2000 dollars. Jennifer leaves; Blaine quits; and the narrator. . . well, that's the seventh day. Easily entertaining and those horse race sequences really hug the rail.