The small lot is empty except for a tree and the make-believe of the two boys who live on either side, which embraces the possibilities that people see in the lot (for a pet shop, a flower shop, a toy shop) before they decide it's too small. But ""What if someone decides our lot isn't too small?"" So they install bushes, a bench and some flowers, and when the first man returns to measure just to make sure. . . ""I can't have a pet shop here,"" he says. ""This lot is a park!"" That's really taking a pocket-park out of your pocket but the boys' imaginings are not inconceivable and the illustrations (qq.v. Ivanov Seven) are a delight; modulated gray washes, crisply delineated, for the street and the city and all that meets the naked eye; fresh, mellifluous color for the fanciful. The contrast carries the message, supplemented by droll detail, and although picture books thrive on empty lots, this is a most attractive property.