MAGGIE COMER ROBINSON, 88, the inspiration for a book and TV documentary, died Tuesday in East Chicago, Ind., of septicemia, a blood infection. Mrs. Robinson was illiterate but insisted her children work hard in school. Her five children earned a total of 13 undergraduate and graduate degrees, and all seven of her grandchildren are college graduates. One son, Dr. James Comer, director of Yale University's Child Study Center, told her life story in Maggie's American Dream: The Life and Times of a Black Family. The book, which chronicled her struggles to raise a family in East Chicago during the 1930s, '40s and '50s, was made into a public television documentary, The Legacy of Maggie's American Dream, which was first broadcast last month.