Meshing their complementary skill sets, physicist David (of Oakland University) and his brother, science fiction writer Richard (Celestial Matter, All of an Instant), explore some of the knottiest problems facing modern cosmologists in this tough but informative primer to modern cosmology. Aside from revealing the science behind the sun, black holes and dark matter, the Garfinkles' demonstrate how science develops, encouraging readers always to ask, "'How do they know that?' as a way of understanding science." The "three steps" of the title begin in the 19th century, when scientists realized that the Earth was, at minimum, millions of years old; they then asked, "How old is the Sun?"-the first sally in a campaign that would unravel the mystery of nuclear energy, reveal how a star becomes a "white dwarf, a neutron star, or a black hole," and spark a fierce, ongoing decades-long debate about the possibility of "black hole evaporation." Arguing that "it is necessary to jump the barrier of user-friendliness and discover the fascinating world beyond that layer of comfort," the Garfinkles aren't afraid to get technical, but this smart, rewarding read is helped by a welcome voice, a feel for narrative and a useful glossary.