The season the ""agonizing reappraisal"" of major league baseball campaigns, good and bad, seems to be in full swing. Recently Jim Brosnan, Cincinnati pitcher, told us how the Reds won the '61 pennant, and now Charlic Elnstein, a professional non-pitching writer, recounts in bloody detail how the San Francisco Giants lost it. From the grossly misleading title the uninitiated might think that the team which attained fame in New York under John McGraw was at least an odds-on favorite to win this year. This isn't true. However, all is not lost for the reader once he's past the title. Mr. Elnstein, who covers the Giants for the San Francisco Chronicle, has written a thorough and perceptive running account of the '61 race, with nice touches of unfabricated humor and in smooth, graphic style that is the hallmark of first-class sports writing. Not everything connected with baseball and its exponents is sweetness and light, but Elnstein's delicate handling of certain matters establishes that he is a veritable gentleman of the press. This is a book for the knowledgeable fan, who can recite the infield fly rule in his sleep. He will be vastly entertained and further educated. Oh yes, Elnstein encourages Giant fans by insisting that Alvin Dark, the church-going aggressive manager, has come of age as a leader and will do better this year. Leave us, as they said at Ebbets Field, hope.