"Publishers' Weekly" called the book "clear, comprehensive, [and] well-researched," noting that it "begins as a vivid and scientifically sound depiction of the age of the giant dinosaurs [and] develops into an impressive tribute to the science of paleontology.Awesome and sometimes spine-chilling as some of the de Camps' descriptions are ... the human story of the first discovery of fossils and the realization of their implications communicates a drama of its own."