FICTION : THE BITTEREST AGE, <i> by Raymond Kennedy (Ticknor & Fields: $22.95; 218 pp.)</i>

Daily, then nightly, the sky is horizon-to-horizon in bombers heading to Berlin, but Ingeborg Maas, 10 years old, stays on. A bomb hits the school; an ancient professor hops through the wreckage, scholastic robes afire, then falls down and dies. But Ingeborg stays on. Potsdam becomes a primary target. The city bucks and heaves and screams. A piano crashes into the basement shelter; the landlady is buried alive. There is no water, no electricity, little food. There is no more wood for coffins. This is the other side of the war, the perspective of ordinary Germans. There are Nazis in Potsdam, to be sure. In the face of invasion, Ingeborg helps an old man, a block warden, to destroy his swastikas, his pictures of Hitler; dazed and befuddled, his sole connection to the world has been a minor post in the party that ignores him. He is hanged. For the most part, though, these are just people struggling to survive, to maintain a little dignity. And there is, memorably, Ingeborg, brave and kind, the sort of youth upon whom postwar hopes are always based.