SPIRIT LAKE (957 pp.)MacKin/ay KantorWorld ($6.95).
Not altogether inaccurately, MacKinlay Kantor's 34th book is billed as a "gigantic novel of the American frontier." Wordier even than Andersonville, Kantor's massive 1956 Pulitzer prizewinner. Spirit Lake is distended by a cast of more than four dozen major characters cursed with total recall and the folksiest dialect since Mr. Dooley. ("Well sakes!'' says one. "Course, I ain't had a touch of shakes since two years agone, and I do firmly believe that it was because I et three hard-boiled eggs on Good Friday last year, and again...