The plight of a conscientious hard-working engine on the verge of retirement is a hackneyed situation in contemporary juvenile fiction, but Miss McGinley gives the old story a fresh twist and sparkling humor. Old Blunderbus -- the last of New York City's double-decker buses, gloriously open to sun and rain on the upper deck, was also the last of the considerate buses who would wait for slow passengers to board, and who was never known to bounce them into each other's laps when starting. But the new sleek single buses with their bad manners were taking over and old Blunderbus's days were numbered. It takes the intervention of the Mayor for whom Blunderbus had once done a favor, to bring the old timer honor and glory in a Transportation parade and an honorable retirement. William Wiesner's buses in black and white and two color have much more personality than the passengers. Nostalgic New Yorkers may weep at a glory gone forever.