THE SAVING GRACE (287 pp.)Mc-Creody HustonLippincott ($3.50).
Change, as it must to all communities, has come to Philadelphia's Main Line, but along the Line can still be found French chateaux bordering colonial farmhouses, Moorish palaces nudging Scottish castles. And the old-style breed of Main Line aristocrat can still be found, holding on. In The Saving Grace, Novelist Mc-Cready Huston conducts a guided tour in the manner of a regional John P. Marquand. At the windup, Novelist Huston's poor but honest working girl has sidetracked her Main Liner into matrimony without even trying.
The girl...