Many political activists will quickly label Heaven's Door, by Harvard economist George Borjas, a vicious attack on America's generous immigration policy. They will have a point: Borjas believes the current level and composition of immigration to the United States does not advance--and arguably harms--American economic and national interests. But they will also miss a very careful argument that neatly places Borjas between the extremes of open-borders advocates and full-scale restrictionists. Borjas, himself an immigrant from Cuba, would cut admissions by about one-third and radically redesign the way in which people gain entry, changing the present system from emphasizing family ties to favoring skills. He bases this reasoning on a series of observations, which he examines in great detail: immigrant earnings lag behind native earnings, there is a clear (and troubling) link between national origin and economic performance, immigration hurts the economic opportunities of poor Americans, and so on. Some readers will think Borjas accentuates the negative; in describing how immigrant skill levels have declined relative to natives, for instance, he downplays the fact that they have risen in an absolute sense. Yet this is an uncommonly clear-headed book on a subject that rouses fiery passions. A country that still considers itself a "nation of immigrants"--and wants to remain one--can't afford to ignore it. --John J. Miller